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This chapter describes the commands used to manage the communication server system and its performance on the network.
For system management configuration tasks and examples, refer to the chapter entitled "Managing the System" in the Access and Communication Servers Configuration Guide.
To enable AAA accounting of requested services for billing or security purposes when using TACACS+, use the aaa accounting global configuration command. Use the no form of this command to disable accounting.
aaa accounting {system | network | connection | exec | command level} {start-stop |
system | Accounting is performed for all system-level events not associated with users, such as reloads. |
network | Accounting is run for all network-related service requests, including SLIP, PPP, PPP NCPs, and ARAP. |
connection | Accounting is run for outbound Telnet and rlogin. |
exec | Accounting is run for Execs (user shells). This may return user profile information such as autocommand information. |
command | Accounting is run for all commands at the specified privilege level. |
level | The command level that should be accounted. Valid entries are 0-15. |
start-stop | A start record accounting notice is sent at the beginning of a process and a stop record is sent at the end of a process. The start accounting record is sent in the background. The requested user process begins regardless of whether or not the start accounting record was received by the accounting server. |
wait-start | As in start-stop, both a start and a stop accounting record are sent to the accounting server. However, if you use the wait-start keyword, the requested user service will not begin until the start accounting record is acknowledged. A stop accounting record will also be sent. |
stop-only | A stop record accounting notice is sent at the end of the requested user process. |
AAA accounting is not enabled.
Global configuration
The aaa accounting command allows you to set start/stop accounting for any or all of the listed functions in the Syntax Description for this command. For minimal accounting control, issue the stop-only command, which sends a stop record accounting notice at the end of the requested user process. For additional accounting control, you can issue the start-stop command, where TACACS+ sends a start accounting notice at the beginning of the requested process and a stop accounting notice at the end of the process. You can further control access and accounting by issuing the wait-start command, which ensures that the start notice is received by the TACACS+ server before granting the user's process request. Accounting is only done to the TACACS+ server.
In the following example, accounting is set for outbound Telnet and rlogin, and both a start and stop accounting notice is sent to the TACACS+ server:
aaa accounting connection start-stop tacacs+
In the following example, accounting is set for privilege level 15 commands, with a wait-start restriction:
aaa accounting command 15 wait-start tacacs+
aaa new-model
aaa authorization
To enable an AAA authentication method for ARA users while using TACACS+, use the aaa authentication arap command. Use the no form of the command to disable this authentication.
aaa authentication arap {default | list-name} method1 [...[method4]]
default | Makes the listed methods that follow this argument the default list of methods used when a user logs in. |
list-name | A character string used to name the following list of authentication methods tried when a user logs in. |
method | One of the methods described in Table 5-1. |
If the default list is not set, only the local user database is checked. This has the same effect as issuing the following command:
aaa authentication arap default local
Global configuration
The list names and default that you set using the aaa authentication arap command are used with the arap authentication command. These lists can contain up to four authentication methods that will be used when a user tries to log in with ARA.
Create a list by entering the aaa authentication arap list-name method command, where list-name is any character string used to name this list, such as MIS-access. The method keyword refers to the list of methods the authentication algorithm will try, in the given sequence. You can enter up to four methods, which are described in Table 5-1.
To create a default list that will be used if no list is specified in the arap authentication command, use the default keyword followed by the methods you wish to be used in default situations.
The additional methods of authentication will only be used if the previous method returns an error, not if it fails.
Use the write terminal command to view lists of authentication methods.
| Method | Description |
|---|---|
if-needed | Will not authenticate if the user has already been authenticated on a TTY line. |
line | Uses the line password for authentication. |
local | Uses the local username database for authentication. |
tacacs+ | Uses TACACS+ authentication. |
The following example creates a list called MIS-access, which first tries TACACS+ authentication and then none:
aaa authentication arap MIS-access tacacs+ none
The following example creates the same list, but sets it as the default list, which will be used for all arap authentications if no other list is specified:
aaa authentication arap default tacacs+ none
A dagger (†) indicates that the command is documented in another chapter.
aaa authentication local-override
aaa new-model
arap authentication†
To enable AAA authentication to determine if a user can access the privileged command level with TACACS+, use the aaa authentication enable default command. Use the no form of the command to disable this authorization method.
aaa authentication enable default method1 [...[method4]]
method | At least one and up to four of the methods described in Table 5-2. |
If the default list is not set, the action will be to check only the enable password. This has the same effect as issuing the following command:
aaa authentication enable default enable
On the console, the enable password is used if it exists. If no password is set, the process will succeed anyway.
Global configuration
Use the aaa authentication enable default command to create a series of authentication methods that are used to determine if a user can access privileged command level. You can specify up to four authentication methods. Method keywords are described in Table 5-2. The additional methods of authentication will only be used if the previous method returns an error, not if it fails. To specify that the authentication should succeed even if all methods return an error, specify none as the final method in the command line.
If a default authentication routine is not set for a function, the default is none—no authentication is performed. Use the write terminal command to view currently configured lists of authentication methods.
| Method | Description |
|---|---|
enable | Uses the enable password for authentication. |
line | Uses the line password for authentication. |
none | Uses no authentication. |
tacacs+ | Uses TACACS+ authentication. |
The following example creates an authentication list that will first try to contact a TACACS+ server. If no server can be found, then AAA will try to use the enable password. If this also returns an error (because no enable password is configured on the server), the user will be allowed access with no authentication.
aaa authentication enable default tacacs+ enable none
A dagger (†) indicates that the command is documented in another chapter.
aaa authentication local-override
aaa new-model
aaa authorization
enable password†
To set AAA authentication at login when using TACACS+, use the aaa authentication login global configuration command. Use the no form of the command to disable AAA authentication.
aaa authentication login {default | list-name} method1 [...[method4]]
default | Makes the listed authentication methods that follow this argument the default list of methods used when a user logs in. |
list-name | A character string used to name the following list of authentication methods tried when a user logs in. |
method | At least one and up to four of the methods described in Table 5-3. |
If the default list is not set, only the local user database is checked. This has the same effect as issuing the following command:
aaa authentication login default local
Global configuration
The default and optional list names that you create with the aaa authentication login command are used with the login authentication command.
Create a list by entering the aaa authentication list-name method command, where list-name is any character string used to name this list, such as MIS-access. The method keyword refers to the list of methods the authentication algorithm tries, in the given sequence. Method keywords are described in Table 5-3.
To create a default list that is used if no list is assigned to a line with the login authentication command, use the default argument followed by the methods you want in default situations.
The additional methods of authentication is only be used if the previous method returns an error, not if it fails. To specify that the authentication should succeed even if all methods return an error, specify none as the final method in the command line.
If authentication is not specifically set for a line, the default is to deny access—no authentication is performed. Use the write terminal command to view currently configured lists of authentication methods.
| Method | Description |
|---|---|
enable | Uses the enable password for authentication. |
line | Uses the line password for authentication. |
local | Uses the local username database for authentication. |
none | Uses no authentication. |
tacacs+ | Uses TACACS+ authentication. |
The following example creates an AAA authentication list called MIS-access. This authentication will first try to contact a TACACS+ server. If no server is found, TACACS+ will return an error and AAA will try to use the enable password. If this also returns an error (because no enable password is configured on the server), the user is allowed access with no authentication.
aaa authentication login MIS-access tacacs+ enable none
The following example creates the same list, but sets it as the default list that will be used for all login authentications if no other list is specified:
aaa authentication login default tacacs+ enable none
A dagger (†) indicates that the command is documented in another chapter.
aaa authentication local-override
aaa new-model
login authentication†
To have the communication server check the local user database for authentication before attempting another form of authentication, use the aaa authentication local-override command. Use the no form of the command to disable the override.
aaa authentication local-overrideThis command has no arguments or keywords.
Override is disabled.
Global configuration
This command is useful when you want to configure an override to the normal authentication process for certain personnel such as system administrators.
When this override is set, the user is always be prompted for the username. The system then checks to see if the entered username corresponds to a local account. If the username does not correspond to one in the local database, login proceeds with the methods configured using other aaa commands (such as aaa authentication login). Note that when using this command, the first prompt is fixed as Username:
The following example enables aaa authentication override:
aaa authentication local-override
aaa authentication arap
aaa authentication enable default
aaa authentication login
aaa new-model
aaa authentication ppp
To specify one or more AAA authentication methods for use on serial interfaces running PPP when using TACACS+, use the aaa authentication ppp command. Use the no form of the command to disable authentication.
aaa authentication ppp {default | list-name} method1 [...[method4]]
default | Makes the listed authentication methods that follow this argument the default list of methods used when a user logs in. |
list-name | A character string used to name the following list of authentication methods tried when a user logs in. |
method | At least one and up to four of the methods described in Table 5-4. |
If the default list is not set, the action will be to check only the local user database. This has the same effect as issuing the following command:
aaa authentication ppp default local
Global configuration
The lists that you create using the aaa authentication ppp command are used with the ppp authentication command. These lists contain up to four authentication methods that will be used when a user tries to log in to the serial interface.
Create a list by entering the aaa authentication ppp list-name method command, where list-name is any character string used to name this list, such as MIS-access. The method keyword refers to the list of methods the authentication algorithm tries, in the given sequence. You can enter up to four methods. Method keywords are described in Table 5-4.
The additional methods of authentication are only used if the previous method returns an error, not if it fails. Specify none as the final method in the command line to have authentication succeed even if all methods return an error.
If authentication is not specifically set for a function, the default is none—no authentication is performed. Use the write terminal command to view lists of authentication methods.
| Method | Description |
|---|---|
if-needed | Does not authenticate if user has already been authenticated on a TTY line. |
local | Uses the local username database for authentication. |
none | Uses no authentication. |
tacacs+ | Uses TACACS+ authentication. |
The following example creates an AAA authentication list called MIS-access for serial lines that use PPP. This authentication first tries to contact a TACACS+ server. If this returns an error, the user is allowed access with no authentication.
aaa authentication MIS-access ppp tacacs+ none
A dagger (†) indicates that the command is documented in another chapter.
aaa authentication local-override
aaa new-model
ppp authentication†
To set parameters that restrict a user's network access based on TACACS+ authorization, use the aaa authorization command. To disable authorization for a function, use the no form of the command.
aaa authorization {network | connection | exec | command level} methods
network | Authorization is run for all network-related service requests, including SLIP, PPP, PPP NCPs, and ARAP. |
connection | Authorization is run for outbound Telnet and rlogin. |
exec | Authorization is run to determine if the user is allowed to run an Exec shell. This may return user profile information such as autocommand information. |
command | Authorization is run for all commands at the specified privilege level. |
level | Specific command level that should be authorized. Valid entries are 0-15. |
Authorization is disabled for all actions (equivalent to the keyword none).
Global configuration
Use the aaa authorization command to create a list of one and up to four authorization methods that can be used when a user accesses the specified function. Table 5-5 lists the different authorization methods.
The additional methods of authorization are only used if the previous method returns an error, not if it fails. Specify none as the final method in the command line to have authorization succeed even if all methods return an error.
| Keyword | Description |
|---|---|
methods |
|
If authorization is not specifically set for a function, the default is none—no authorization is performed.
The following example specifies that TACACS+-style authorization is used for all network-related requests. If this authorization method returns an error (if the TACACS+ server cannot be contacted), no authorization is performed, and the request is successful.
aaa authorization network tacacs+ none
The following example specifies that TACACS+-style authorization is run for level 15 commands. If this authorization method returns an error (if the TACACS+ server cannot be contacted), no authorization is performed, and the request succeeds.
aaa authorization command 15 tacacs+ none
aaa accounting
aaa new-model
To enable the new AAA access control model that includes TACACS+, issue the aaa new-model global configuration command. Use the no form of the command to disable this functionality.
aaa new-modelThis command has no arguments or keywords.
AAA/TACACS+ is not enabled.
Global configuration
This command enables the new AAA access control system and TACACS+. If you initialize this functionality and later decide to use TACACS or XTACACS, issue the no version of this command and then enable the version of TACACS you want to use.
The following example initializes AAA and TACACS+:
aaa new-model
aaa accounting
aaa authentication arap
aaa authentication enable default
aaa authentication local-override
aaa authentication login
aaa authentication ppp
aaa authorization
To create a command alias, use the alias global configuration command. Use the no alias command to delete all aliases in a command mode or to delete a specific alias, and to revert to the original command syntax.
alias mode alias-name alias-command-line
mode | Command mode of the original command and alias commands. See Table 5-6 for a list of options for this argument. |
alias-name | Command alias. |
alias-command-line | Original command syntax. |
Default aliases are in EXEC mode as follows:
| Command Alias | Original Command |
|---|---|
h | help |
lo | logout |
p | ping |
r | resume |
s | show |
w | where |
Global configuration
You can use simple words as aliases or abbreviations. The aliases in the Default section are predefined. They can be turned off using the no alias command.
Table 5-6 shows the acceptable options for the mode argument in the alias global configuration command.
| Argument Options | Mode |
|---|---|
configuration | Global configuration |
controller | Controller configuration |
exec | EXEC |
hub | Hub configuration |
interface | Interface configuration |
ipx-router | IPX router configuration |
line | Line configuration |
map-class | Map class configuration |
map-list | Map list configuration |
route-map | Route map configuration |
router | Router configuration |
See the summary of command modes in the user interface chapter in the Access and Communication Configuration Guide for more information about command modes.
When you use online help, command aliases are indicated by an asterisk (*), as follows:
cs#lo?
*lo=logout lock login logout
When you use online help, aliases that contain spaces (for example, "telnet device.cisco.com 25") are displayed as follows:
cs# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
cs(config)# alias exec device-mail telnet device.cisco.com 25
cs(config)# end
cs#device-mail?
*device-mail="telnet device.cisco.com 25"
When you use online help, the alias is expanded and replaced with the original command, as shown in the following example with the "td" alias:
cs(config)#alias exec td trace device
cs(config)#^Z
cs#t?
*td="trace device" telnet terminal test tn3270
trace
To list only commands and omit aliases, begin your input line with a space. In the following example, the alias td is not shown, because there is a space before the t? command line.
cs# t?
telnet terminal test tn3270 trace
As with commands, you can use online help to display the arguments and keywords that can follow a command alias. In the following example, the alias td is created to represent the command telnet device. The /debug and /line switches can be added to telnet device to modify the command:
cs(config)# alias exec td telnet device
cs(config)# ^Z
cs#td ?
/debug Enable telnet debugging mode
/line Enable telnet line mode
...
whois Whois port
<cr>
cs# telnet device
You must enter the complete syntax for the alias command. Partial syntax for aliases are not accepted. In the following example, the parser does not recognize the command t as indicating the alias td.
bones# t
% Ambiguous command: "t"
In the following example, the alias fixmyrt is created for the EXEC-mode command clear ip route 198.92.116.16.
alias exec fixmyrt clear ip route 198.92.116.16
show aliases
To enable TACACS+ authentication for ARA on a line, use the arap authentication command. Use the no form of the command to disable authentication for an ARA line.
arap authentication {default | list-name}
default | Use the default list created with the aaa authentication arap command. |
list-name | Use the indicated list created with the aaa authentication arap command. |
ARAP authentication uses the default set with aaa authentication arap command. If no default has been set, the local user database is checked.
Line configuration
This command is a per-line command, and specifies the name of a list of AAA authentication methods to try at login. If no list is specified, the default list will be used (whether or not it is specified in the command line). Defaults and lists are created by using the aaa authentication arap command. Entering the no version of arap authentication has the same effect as entering the command with the default argument.
Before issuing this command, create a list of authentication processes by using the aaa authentication arap global configuration command.
 | Caution If you use a list-name that was not configured with the aaa authentication arap command, ARAP will be disabled on this line. |
The following example specifies that the TACACS+ authentication list called MIS-access is used on ARA line 7:
line 7
arap authentication MIS-access
aaa authentication arap
Use the buffers global configuration command to make adjustments to initial buffer pool settings and to the limits at which temporary buffers are created and destroyed. Use the no buffers command to return the buffers to their default size.
buffers {small | middle | big | large | huge | interface-type interface-number} {permanent |
small | Small buffer size. |
middle | Medium buffer size. |
big | Big buffer size. |
large | Large buffer size. |
huge | Huge buffer size. |
interface-type | Interface type of the interface buffer pool. |
interface-number | Interface number of the interface buffer pool. |
permanent | Number of permanent buffers that the system tries to allocate. Permanent buffers are normally not deallocated by the system. |
max-free | Maximum number of free or unallocated buffers in a buffer pool. |
min-free | Minimum number of free or unallocated buffers in a buffer pool. |
initial | Number of additional temporary buffers that should be allocated when the system is reloaded. This can be used to ensure that the system has necessary buffers immediately after reloading in a high-traffic environment. |
number | Number of buffers to be allocated. |
The default number of the buffers in a pool is determined by the hardware configuration and can be displayed with the EXEC show buffers command.
Global configuration
It is normally not necessary to adjust these parameters; do so only after consulting with technical support personnel. Improper settings could adversely impact system performance.
Buffer pool allocation is a user tunable parameter. The buffer pool to tune depends on the type of encapsulation used by the interfaces. Correspondingly, the ring size changes with the size of the buffer required.
In the following example, the system will try to keep at least 50 small buffers free:
buffers small min-free 50
In the following example, the permanent buffer pool allocation for big buffers is increased to 200. On a Cisco 2509 1E2T box using HDLC encapsulation, there are four receive rings, each of 32 entries. The cache size is 32 buffers. The MTU for this sort of encapsulation is below 1524 bytes (the same as for Ethernet) which means that you must use buffers from the "big" pool. The basic number of "big" buffers required is (2 + 1) * 32 = 96. Adding a bit of "comfort" space, the following command can then be used:
buffers big permanent 100
The above example shows approximate figures.
In the following example, the initial and permanent interface buffer pools are set to 100:
buffers ethernet 0 initial 100
buffers ethernet 0 permanent 100
buffers huge size
show buffers
Use the buffers huge size global configuration command to dynamically resize all huge buffers to the value you specify. Use the no buffers huge size command to restore the default buffer values.
buffers huge size number
number | Number of buffers to be allocated |
18024 buffers
Global configuration
Use this command only after consulting with technical support personnel. The buffer size cannot be lowered below the default.
In the following example, the system will resize huge buffers to 20000 bytes:
buffers huge size 20000
buffers
show buffers
To enable CDP on an interface, use the cdp enable interface configuration command. Use the no cdp enable command to disable CDP on an interface.
cdp enableThis command has no arguments or keywords.
Disabled
Interface configuration
CDP is enabled by default at the global level, but it must be enabled on each interface in order to send or receive CDP information.
In the following example, CDP is enabled on Ethernet interface 0:
interface ethernet 0
cdp enable
cdp run
To specify the amount of time the receiving device should hold a CDP packet from your communication server before discarding it, use the cdp holdtime global configuration command. Use the no cdp holdtime command to revert to the default setting.
cdp holdtime seconds
seconds | Specifies the hold time to be sent in the CDP update packets. |
180 seconds
Global configuration
CDP packets are sent with time-to-live, or hold time, that is nonzero after an interface is enabled and a hold time of 0 immediately before an interface is idled down.
The CDP hold time must be set to a higher number of seconds than the time between CDP transmissions, which is set using the cdp timer command.
In the following example, the CDP packets being sent from your device should be held by the receiving device for 60 seconds before being discarded. You might want to set the hold time lower than the default setting of 180 seconds if information about your device changes often and you want the receiving devices to purge this information more quickly.
cdp holdtime 60
cdp timer
show cdp
To enable CDP on your communication server, use the cdp run global configuration command. Use the no cdp run command to disable CDP.
cdp runThis command has no arguments or keywords.
Enabled
Global configuration
CDP is enabled on your communication server by default, which means the communication server will receive CDP information. However, to receive CDP packets it must be enabled on interfaces, using the cdp enable interface configuration command.
In the following example, CDP is disabled for the communication server.
no cdp run
cdp enable
To specify how often your communication server will send CDP updates, use the cdp timer global configuration command. Use the no cdp timer command to revert to the default setting.
cdp timer seconds
seconds | Specifies how often your communication server will send CDP updates. |
60 seconds
Global configuration
The trade-off with sending more frequent transmissions is providing up-to-date information versus using bandwidth more often.
In the following example, CDP updates will be sent from your communication server every 80 seconds, less frequently than the default setting of 60 seconds. You might want to make this change if you are concerned about preserving bandwidth.
cdp timer 80
cdp holdtime
show cdp
To reset CDP traffic counters to zero (0) on your communication server, use the clear cdp counters privileged EXEC command.
clear cdp countersThis command has no arguments or keywords.
Privileged EXEC
In the following example, the CDP counters have been cleared. The show cdp traffic output shows that all of the traffic counters have been reset to zero (0).
cs# clear cdp counters
cs# show cdp traffic
CDP counters :
Packets output: 0, Input: 0
Hdr syntax: 0, Chksum error: 0, Encaps failed: 0
No memory: 0, Invalid packet: 0, Fragmented: 0
show cdp traffic
clear cdp table
To clear the table that contains CDP information about neighbors, use the clear cdp table privileged EXEC command.
clear cdp tableThis command has no arguments or keywords.
Privileged EXEC
In the following example, the CDP table is cleared. The output of the show cdp neighbors command shows that all information has been deleted from the table.
cs# clear cdp table
CDP-AD: Deleted table entry for neon.cisco.com, interface Ethernet0
CDP-AD: Deleted table entry for neon.cisco.com, interface Serial0
cs# show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP
Device ID Local Intrfce Holdtme Capability Platform Port ID
clear cdp counters
show cdp neighbors
To manually set the system clock, use the clock set EXEC command.
clock set hh:mm:ss day month year
hh:mm:ss | Current time in hours (military format), minutes, and seconds |
day | Current day (by date) in the month |
month | Current month (by name) |
year | Current year (no abbreviation) |
EXEC
Generally, if the system is synchronized by a valid outside timing mechanism, such as an NTP clock source, you need not set the system clock. Use this command if no other time sources are available. The time specified in this command is relative to the configured time zone.
In the following example, the system clock is manually set to 1:32 p.m. on July 23, 1993:
clock set 13:32:00 23 July 1993
calendar set
clock read-calendar
clock summer-time
clock timezone
To configure the system to switch to summer time (daylight savings time) automatically, use one of the formats of the clock summer-time global configuration command. Use the no form of this command to configure the communication server not to automatically switch to summer time.
clock summer-time zone recurring [week day month hh:mm week day month hh:mm [offset]]
zone | Name of the time zone (PDT, ...) to be displayed when summer time is in effect |
week | Week of the month (1 to 5 or last) |
day | Day of the week (Sunday, Monday ) |
date | Date of the month (1 to 31) |
month | Month (January, February, ) |
year | Year (1993 to 2035) |
hh:mm | Time (military format) in hours and minutes |
offset | (Optional) Number of minutes to add during summer time (default is 60) |
Summer time is disabled. If clock summer-time zone recurring is specified without parameters, the summer time rules default to United States rules. Default of offset is 60.
Global configuration
Use this command if you want to automatically switch to summer time (for display purposes only). Use the recurring form of the command if the local summer time rules are of this form. Use the date form to specify a start and end date for summer time if you cannot use the first form.
In both forms of the command, the first part of the command specifies when summer time begins, and the second part specifies when it ends. All times are relative to the local time zone. The start time is relative to standard time. The end time is relative to summer time. If the starting month is after the ending month, the system assumes that you are in the Southern Hemisphere.
In the following example, summer time starts on the first Sunday in April at 02:00 and ends on the last Sunday in October at 02:00:
clock summer-time PDT recurring 1 Sunday April 2:00 last Sunday October 2:00
If you live in a place where summer time does not follow the pattern in the first example, you could set it to start on October 12, 1993 at 02:00, and end on April 28, 1994 at 02:00, with the following example:
clock summer-time date 12 October 1993 2:00 28 April 1994 2:00
calendar set
clock timezone
To set the time zone for display purposes, use the clock timezone global configuration command. To set the time to Coordinated Universal Time (UTC), use the no clock timezone command.
clock timezone zone hours [minutes]
zone | Name of the time zone to be displayed when standard time is in effect |
hours | Hours offset from UTC |
minutes | (Optional) Minutes offset from UTC |
UTC
Global configuration
The system internally keeps time in UTC, so this command is used only for display purposes and when the time is manually set.
In the following example, the time zone is set to Pacific Standard Time and is offset 8 hours behind UTC:
clock timezone PST -8
calendar set
clock set
clock summer-time
show clock
To assign a custom queue list to an interface, use the custom-queue-list interface configuration command. To remove a specific list or all list assignments, use the no form of this command.
custom-queue-list list
list | Number of the custom queue list you want to assign to the interface. An integer from 1 to 10. |
No custom queue list is assigned.
Interface configuration
You can assign only one queue list per interface. Use this command in place of the priority-list command (not in addition to it). Custom queuing allows a fairness that is not provided with priority queuing. With custom queuing, you can control the interfaces' available bandwidth when it is unable to accommodate the aggregate traffic enqueued. Associated with each output queue is a configurable byte count, which specifies how many bytes of data should be delivered from the current queue by the system before the system moves on to the next queue. When a particular queue is being processed, packets are sent until the number of bytes sent exceeds the queue byte count or until the queue is empty.
In the following example, custom queue list number 3 is assigned to serial interface 0:
interface serial 0
custom-queue-list 3
queue-list default
queue-list interface
queue-list protocol
queue-list queue byte-count
queue-list queue limit
queue-list stun
To have the access server try to generate a configuration that is compatible with an earlier Cisco IOS release, use the downward-compatible-config global configuration command. To remove this feature, use the no form of this command.
downward-compatible-config version
version | Cisco IOS Release number, not earlier than 10.2. |
Disabled
Global configuration
In Cisco IOS Release 10.3, IP access lists changed format. Use this command to regenerate a configuration in a format prior to Release 10.3 if you are going to downgrade from a Release 10.3 or later to an earlier release. The earliest release this command accepts is 10.2.
When this command is configured, the router attempts to generate a configuration that is compatible with the specified version. Currently, this command affects only IP access lists.
Under some circumstances, the software might not be able to generate a fully backward-compatible configuration. In such a case, the software issues a warning message whenever it tries to write a configuration that is not downward compatible.
The following example, the router will attempt to generate a configuration file compatible with Cisco IOS Release 10.2:
downward-compatible-config 10.2
A dagger (†) indicates that the command is documented in another chapter.
access-list (extended)†
access-list (standard)†
To specify what happens if the TACACS servers used by the enable command do not respond, use the enable last-resort global configuration command. The no form of this command restores the default.
enable last-resort {password | succeed}
password | Allows users to enable by entering the privileged command level password. |
succeed | Allows users to enable without further question. |
Default action is to fail.
Global configuration
The secondary authentication is used only if the first attempt failed. The second authentication will not occur if the first authentication was only unsuccessful.
In the following example, if the TACACS servers do not respond to the enable command, the user can enable by entering the privileged level password:
enable last-resort password
A dagger (†) indicates that the command is documented in another chapter.
enable †
Use the enable password global configuration command to set a local password to control access to various privilege levels. Use the no form of this command to remove the password requirement.
enable password [level level] {password}
level level | (Optional) Level for which the password applies. You can specify up to sixteen privilege levels, using numbers 0 through 15. Level 1 is normal EXEC-mode user privileges. If this argument is not specified, the privilege level defaults to 15 (traditional enable privileges). The same holds true for the no form of the command. |
password | The enable password password as you would type it when enabling. This password should be different from the password created with the enable secret command. If you have the service password-encryption flag set, when the router displays the password for you later it will be displayed encrypted (an encrypted form of what you typed). |
encryption-type | (Optional) The Cisco-proprietary algorithm used to encrypt the password. Currently the only encryption type available is 7 . If you specify encryption-type, the next argument you supply must be an encrypted password (a password already encrypted by a Cisco router). |
encrypted-password | An encrypted password you enter, copied from another router configuration. |
No password is defined.
Global configuration
You will not ordinarily enter an encryption type. Typically you enter an encryption type only if you copy and paste back into this command a password that has already been encrypted by a Cisco router.
Use this command with the level option to define a password for a specific privilege level. Once the level and the password are specified, give the password to the users you want to have access at this level. Use the privilege level (global) configuration command to specify commands accessible at various level.
Enable or disable password encryption with the service password-encryption command.
An enable password can contain from 1 to 80 uppercase and lowercase alphanumeric characters. The first character cannot be a number. Some spaces are valid password characters; for example, "two words" is valid. Leading spaces are ignored, but trailing spaces are recognized. For example "woolly" is interpreted as "woolly" (without the space), while "woolly " is interpreted as "woolly " (with the space). To create an enable password containing a question mark (?), precede the question mark with the keystrokes Ctrl-V. For example, to create the password "abc?123", you enter the letters abc followed by Ctrl-V followed by ? followed by the numbers 123. When the system prompts you to enter the enable password, you need not precede the question mark with the Ctrl-V; you can simply enter abc?123 at the password prompt.
In the following example, the password pswd2 is enabled for privilege level 2:
enable password level 2 pswd2
In the following example the encrypted password Xyti5Rkls3LoyxzS8t9, which has been copied from a router configuration file, is set for privilege level 2 using encryption type 7:
enable password level 2 7 Xyti5Rkls3LoyxzS8t9
A dagger (†) indicates that the command is documented outside this chapter.
disable †
enable †
privilege level (global)
service password-encryption
show privilege
Use the enable secret command to specify an additional layer of security over the enable password command. Use the no form of the command to turn off the enable secret function.
enable secret [level level] {password}
level level | (Optional) Level for which the password applies. You can specify up to sixteen privilege levels, using numbers 0 through 15. Level 1 is normal EXEC-mode user privileges. If this argument is not specified, the privilege level defaults to 15 (traditional enable privileges). The same holds true for the no form of the command. |
password | The enable secret password—the password you would type when enabling. This password should be different from the password created with the enable password command. When the router displays the password for you later, it will be displayed encrypted (an encrypted form of what you typed). |
encryption-type | (Optional) The Cisco-proprietary algorithm used to encrypt the password. Current the only encryption type available for this command is 5 . If you specify encryption-type, the next argument you supply must be an encrypted password (a password encrypted by a Cisco router). |
encrypted password | An encrypted password you enter, copied from another router configuration. |
Disabled
Global configuration
You will not ordinarily enter an encryption type. Typically you enter an encryption type only if you paste back into this command an encrypted password that you copied from a router configuration file.
The enable secret command is used in conjunction with the enable password command to provide an additional layer of security over the enable password. This scheme provides better security by storing the enable secret using a non-reversible cryptographic function.
This added layer of security is useful in environments where the password crosses the network or is stored on a TFTP server.
If you use the same password for enable password and enable secret, you receive an error message warning that this practice is not recommended; but the password will be accepted. By using the same password, however, you undermine the additional security the enable secret command provides.
The following example specifies an enable secret password of gobbledegook:
enable secret gobbledegook
After specifying an enable secret password, users must enter this password to gain access. Any passwords set through enable password will no longer work.
Password: gobbledegook
In the following example the encrypted password Xyti5Rkls3LoyxzS8t9, which has been copied from a router configuration file, is enabled for privilege level 2 using encryption type 5:
enable password level 2 5 $1$FaD0$Xyti5Rkls3LoyxzS8t98j2
A dagger (†) indicates that the command is documented outside this chapter.
enable †
enable password
To enable use of TACACS to determine whether a user can access the privileged command level, use the enable use-tacacs global configuration command. Use the no enable use-tacacs command to disable TACACS verification.
enable use-tacacsThis command has no arguments or keywords.
Disabled
Global configuration
When you add this command to the configuration file, the EXEC enable command prompts for a new username and password pair. This pair is then passed to the TACACS server for authentication. If you are using extended TACACS, it also will pass any already-existing UNIX user identification code to the server.
| Caution If you use the enable use-tacacs command, you must also use the tacacs-server authenticate enable command, or else you will be locked out of the communication server. |
The following example sets TACACS verification on the privileged EXEC-level login sequence:
enable use-tacacs
tacacs-server authenticate enable
tacacs-server authenticate enable
To specify or modify the host name for the network server, use the hostname global configuration command.
hostname name
name | New host name for the network server; the name is case sensitive. |
The factory-assigned default host name is cs.
Global configuration
The order of display at startup is the message-of-the-day (MOTD) banner, then login and password prompts, then the EXEC banner.
The host name is used in prompts and default configuration filenames. The setup command facility also prompts for a host name at startup.
The following example changes the host name to sandbox:
hostname sandbox
seconds | Length of time for which data is used to compute load statistics. A value that is a multiple of thirty, between 30 and 600 (30, 60, 90, 120, and so forth). |
300 seconds (or 5 minutes)
Interface configuration
If you want load computations to be more reactive to short bursts of traffic rather than averaged over five-minute periods, you can shorten the length of time over which load averages are computed.
If the load interval is set to thirty seconds, new data is used for load calculations over a thirty-second period. This data is used to compute load statistics, including input rate in bits and packets per second, output rate in bits and packets per second, load, and reliability.
Load data is gathered every five seconds on the communication server. This data is used for a weighted average calculation in which more-recent load data has more weight in the computation than older load data. If the load interval is set to thirty seconds, the average is computed for the last thirty seconds of load data.
The load-interval command allows you to change the default interval five minutes to a shorter or longer period of time. If you change it to a shorter period of time, the input and output statistics that are displayed when you use the show interface command will be more current and based on more instantaneous data rather than reflecting a more average load over a longer period of time.
This command is often used for dial backup purposes to increase or decrease the likelihood of a backup interface being implemented, but it can be used on any interface.
In the following example, the default five-minute average is set it to a thirty-second average. A burst in traffic that would not trigger a dial backup for an interface configured with the default five-minute interval might trigger a dial backup for this interface that is set for a shorter, thirty-second interval.
interface serial 0
load-interval 30
show interface
To log messages to a syslog server host, use the logging global configuration command. The no logging command deletes the syslog server with the specified address from the list of syslogs.
logging host
host | Name or IP address of the host to be used as a syslog server |
No messages are logged to a syslog server host.
Global configuration
This command identifies a syslog server host to receive logging messages. By issuing this command more than once, you build a list of syslog servers that receive logging messages.
The following example logs messages to a host named johnson:
logging johnson
logging trap
service timestamps
To log messages to an internal buffer, use the logging buffered global configuration command. The no logging buffered command cancels the use of the buffer and writes messages to the console terminal, which is the default.
logging bufferedThis command has no arguments or keywords.
The communication server displays all messages to the console terminal.
Global configuration
This command copies logging messages to an internal buffer instead of writing them to the console terminal. The buffer is circular in nature, so newer messages overwrite older messages.
To display the messages that are logged in the buffer, use the EXEC command show logging. The first message displayed is the oldest message in the buffer.
The following example illustrates how to enable logging to an internal buffer:
logging buffered
To limit messages logged to the console based on severity, use the logging console global configuration command. To disable logging to the console terminal, use the no form of the command.
logging console level
level | Limits the logging of messages displayed on the console terminal to the specified level and levels below it. See Table 5-7 for a list of the level keywords. |
The debugging level
Global configuration
Specifying one of the level names shown in Table 5-7 causes messages at that level and numerically lower levels to be displayed at the console terminal.
The EXEC command show logging displays the addresses and levels associated with the current logging setup, as well as any other logging statistics.
| Level Name | Level | Description | Syslog Definition |
|---|---|---|---|
emergencies | 0 | System unusable | LOG_EMERG |
alerts | 1 | Immediate action needed | LOG_ALERT |
critical | 2 | Critical conditions | LOG_CRIT |
errors | 3 | Error conditions | LOG_ERR |
warnings | 4 | Warning conditions | LOG_WARNING |
notifications | 5 | Normal but significant condition | LOG_NOTICE |
informational | 6 | Informational messages only | LOG_INFO |
debugging | 7 | Debugging messages | LOG_DEBUG |
The following example changes the level of messages displayed to the console terminal to alerts, which means alerts and emergencies are displayed:
logging console alerts
logging facility
To configure the syslog facility in which error messages are sent, use the logging facility global configuration command. To revert to the default of local7, use the no form of this command.
logging facility facility-type
facility-type | Logging facility type. See Table 5-8 for the facility-type keywords. |
local7
Global configuration
| Keyword | Description |
|---|---|
auth | Authorization system |
cron | Cron facility |
daemon | System daemon |
kern | Kernel |
local0-7 | Reserved for locally defined messages |
lpr | Line printer system |
Mail system | |
news | USENET news |
sys9 | System use |
sys10 | System use |
sys11 | System use |
sys12 | System use |
sys13 | System use |
sys14 | System use |
syslog | System log |
user | User process |
uucp | UNIX-to-UNIX copy system |
The following example configures the syslog facility to Kernel:
logging facility kern
logging console
To limit messages logged to the terminal lines (monitors) based on severity, use the logging monitor global configuration command. Use the no form of this command to disable logging to terminal lines other than the console line.
logging monitor level
level | One of the level keywords listed in Table 5-7 |
debugging
Global configuration
Specifying a level causes messages at that level and numerically lower levels to be displayed to the monitor.
This command limits the logging messages displayed on terminal lines other than the console line to messages with a level at or above the specified level.
The following example specifies that only messages of the levels errors, critical, alerts, and emergencies be displayed on terminals:
logging monitor errors
A dagger (†) indicates that the command is documented in another chapter.
terminal monitor †
To control logging of error messages, use the logging on global configuration command. This command enables or disables message logging to all destinations except the console terminal. The no logging on command enables logging to the console terminal only.
logging onThis command has no arguments or keywords.
The communication server logs messages to the console terminal.
Global configuration
The following example shows how to direct error messages to the console terminal only:
no logging on
level severity-level-number | (Optional) Message severity level. Messages with a severity level equal to or higher than this value are printed asynchronously. When specifying a severity level number, consider that for the logging system, low numbers indicate greater severity and high numbers indicate lesser severity. The default value is 2. |
all | (Optional) Specifies that all messages are printed asynchronously, regardless of the severity level. |
limit number-of-buffers | (Optional) Number of buffers to be queued for the terminal after which new messages are dropped. The default value is 20. |
This feature is turned off by default.
If you do not specify a severity level, the default value of 2 is assumed.
If you do not specify the maximum number of buffers to be queued, the default value of 20 is assumed.
Line configuration
When synchronous logging of unsolicited messages and debug output is turned on, unsolicited router output is displayed on the console or printed after solicited router output is displayed or printed. Unsolicited messages and debug output is displayed on the console after the prompt for user input is returned. This is to keep unsolicited messages and debug output from being interspersed with solicited router output and prompts. After the unsolicited messages are displayed, the console displays the user prompt again.
When specifying a severity level number, consider that for the logging system, low numbers indicate greater severity and high numbers indicate lesser severity.
When a terminal line's message-queue limit is reached, new messages are dropped from the line, although these messages might be displayed on other lines. If messages are dropped, the notice "%SYS-3-MSGLOST number-of-messages due to overflow" follows any messages that are displayed. This notice is displayed only on the terminal that lost the messages. It is not sent to any other lines, any logging servers, or the logging buffer.
| Caution By configuring abnormally large message-queue limits and setting the terminal to "terminal monitor" on a terminal that is accessible to intruders, you expose yourself to "denial of service" attacks. An intruder could carry out the attack by putting the terminal in synchronous output mode, making a Telnet connection to a remote host, and leaving the connection idle. This could cause large numbers of messages to be generated and queued, and these messages would consume all available RAM. Although unlikely to occur, you should guard against this type of attack through proper configuration. |
The following example identifies a line and configures synchronous logging for that line, then it does this for another line:
line 0 4
logging synchronous level 6
line 2
logging synchronous level 7 limit 70000
A dagger (†) indicates that the command is documented in another chapter.
line †
To limit messages logged to the syslog servers based on severity, use the logging trap global configuration command. Use the no form of this command to disable logging to syslog servers.
logging trap level
level | One of the level keywords listed in Table 5-7 |
informational
Global configuration
Table 5-7 lists the syslog definitions that correspond to the debugging message levels. Additionally, there are four categories of messages generated by the software, as follows:
Use the logging and logging trap commands to send messages to a UNIX syslog server.
The following example logs messages to a host named johnson and limits messages logged to the syslog server.
logging johnson
logging trap notifications
logging
To enable TACACS+ authentication for logins, use the login authentication command. Use the no form of the command to return to the default.
login authentication {default |list-name}
default | Uses the default list created with the aaa authentication login command. |
list-name | Uses the indicated list created with the aaa authentication login command. |
Uses the default set with aaa authentication login.
Line configuration
This command is a per-line command used with AAA, and specifies the name of a list of TACACS+ authentication methods to try at login. If no list is specified, the default list will be used (whether or not it is specified in the command line). Defaults and lists are created by using the aaa authentication login command. Entering the no version of login authentication has the same effect as entering the command with the default argument.
Before issuing this command, create a list of authentication processes by using the global configuration aaa authentication login command.
| Caution If you use a list-name that was not configured with the aaa authentication login command, you will disable login on this line. |
The following example specifies that the default AAA authentication is to be used on line 4:
line 4
login authentication default
The following example specifies that the AAA authentication list called MIS-access is to be used on line 7:
line 7
login authentication MIS-access
A dagger (†) indicates that the command is documented in another chapter.
aaa authentication login†
To control access to the system's Network Time Protocol (NTP) services, use the ntp access-group global configuration command. To remove access control to the system's NTP services, use the no form of this command.
ntp access-group {query-only | serve-only | serve | peer} access-list-number
query-only | Allows only NTP control queries. See RFC 1305 (NTP version 3). |
serve-only | Allows only time requests. |
serve | Allows time requests and NTP control queries, but does not allow the system to synchronize to the remote system. |
peer | Allows time requests and NTP control queries and allows the system to synchronize to the remote system. |
access-list-number | Number (1 to 99) of a standard IP access list. |
No access control (full access granted to all systems)
Global configuration
The access group options are scanned in the following order from least restrictive to most restrictive:
1. peer
2. serve
3. serve-only
4. query-only
Access is granted for the first match that is found. If no access groups are specified, all access is granted to all sources. If any access groups are specified, only the specified access is granted. This facility provides minimal security for the time services of the system. However, it can be circumvented by a determined programmer. If tighter security is desired, use the NTP authentication facility.
In the following example, the system is configured to allow itself to be synchronized by a peer from access list 99. However, the system restricts access to allow only time requests from access list 42.
ntp access-group peer 99
ntp access-group serve-only 42
A dagger (†) indicates that the command is documented in another chapter.
access-list †
To enable Network Time Protocol (NTP) authentication, use the ntp authenticate global configuration command. Use the no form of this command to disable the feature.
ntp authenticateThis command has no keywords or arguments.
No authentication
Global configuration
Use this command if you want authentication. If this command is specified, the system will not synchronize to a system unless it carries one of the authentication keys specified in the ntp trusted-key command.
The following example enables NTP authentication:
ntp authenticate
ntp authentication-key
ntp trusted-key
To define an authentication key for Network Time Protocol (NTP), use the ntp authentication-key global configuration command. Use the no form of this command to remove the authentication key for NTP.
ntp authentication-key number md5 value
number | Key number (1 to 4294967295) |
md5 | Key type |
value | Key value (an arbitrary string of up to eight characters) |
No authentication key is defined for NTP.
Global configuration
Use this command to define authentication keys for use with other NTP commands in order to provide a higher degree of security. Currently, only the key type md5 is supported.
The following example sets authentication key 10 to aNiceKey:
ntp authentication-key 10 md5 aNiceKey
ntp authenticate
ntp peer
ntp server
ntp trusted-key
To specify that a specific interface should send Network Time Protocol (NTP) broadcast packets, use the ntp broadcast interface configuration command. Use the no form of this command to disable this capability.
ntp broadcast [version number]
version number | (Optional) Number from 1 to 3 indicating the NTP version |
Disabled
Interface configuration
In the following example, Ethernet interface 0 is configured to send NTP version 2 packets:
interface ethernet 0
ntp broadcast version 2
ntp broadcast client
ntp broadcastdelay
To allow the system to receive NTP broadcast packets on an interface, use the ntp broadcast client interface configuration command. Use the no form of this command to disable this capability.
ntp broadcast clientThis command has no arguments or keywords.
Disabled
Interface configuration
Use this command to allow the system to listen to broadcast packets on an interface-by-interface basis.
In the following example, the communication server synchronizes to NTP packets broadcasted on Ethernet interface 1:
interface ethernet 1
ntp broadcast client
ntp broadcast
ntp broadcastdelay
To set the estimated round-trip delay between the communication server and a Network Time Protocol (NTP) broadcast server, use the ntp broadcastdelay global configuration command. Use the no form of this command to revert to the default value.
ntp broadcastdelay microseconds
microseconds | Estimated round-trip time (in microseconds) for NTP broadcasts. The range is from 1 to 999999. |
3000 microseconds
Global configuration
Use this command when the communication server is configured as a broadcast client and the round-trip delay on the network is other than 3000 microseconds.
In the following example, the estimated round-trip delay between the communication server and the broadcast client is set to 5000 microseconds:
ntp broadcastdelay 5000
ntp broadcast
ntp broadcast client
As NTP compensates for the error in the system clock, it keeps track of the correction factor for this error. The system automatically saves this value into the system configuration using the ntp clock-period global configuration command. The system uses the no form of this command to revert to the default.
ntp clock-period value
value | Amount to add to the system clock for each clock hardware tick (in units of |
17179869 (4 milliseconds)
Global configuration
If a write memory command is entered to save the configuration to nonvolatile memory, this command will automatically be added to the configuration. It is a good idea to use the write memory command after NTP has been running for a week or so; this will help NTP synchronize more quickly if the system is restarted.
Do not enter this command; it is documented for informational purposes only. The system automatically generates this command as Network Time Protocol (NTP) determines the clock error and compensates.
To prevent an interface from receiving Network Time Protocol (NTP) packets, use the ntp disable interface configuration command. To enable receipt of NTP packets on an interface, use the no form of this command.
ntp disableThis command has no arguments or keywords.
Enabled
Interface configuration
This command provides a simple method of access control.
In the following example, Ethernet interface 0 is prevented from receiving NTP packets:
interface ethernet 0
ntp disable
To configure the communication server as a Network Time Protocol (NTP) master clock to which peers synchronize themselves when an external NTP source is not available, use the ntp master global configuration command. To disable the master clock function, use the no ntp master command.
ntp master [stratum]
stratum | (Optional) Number from 1 to 15. Indicates the NTP stratum number that the system will claim. |
By default, the master clock function is disabled. When enabled, the default stratum is 8.
Global configuration
Because our implementation of NTP does not support directly attached radio or atomic clocks, the communication server is normally synchronized, directly or indirectly, to an external system that has such a clock. In a network without Internet connectivity, such a time source may not be available. The ntp master command is used in such cases.
If the communication server has ntp master configured, and it cannot reach any clock with a lower stratum number, the communication server will claim to be synchronized at the configured stratum number, and other communication servers will be willing to synchronize to it via NTP.
| Caution Use this command with extreme caution. It is very easy to override valid time sources using this command, especially if a low stratum number is configured. Configuring multiple machines in the same network with the ntp master command can cause instability in timekeeping if the machines do not agree on the time. |
In the following example, the communication server is configured as an NTP master clock to which peers can synchronize:
ntp master 10
clock calendar-valid
To configure the communication server's system clock to synchronize a peer or to be synchronized by a peer, use the ntp peer global configuration command. To disable this capability, use the no form of this command.
ntp peer ip-address [version number] [key keyid] [source interface] [prefer]
ip-address | IP address of the peer providing, or being provided, the clock synchronization. |
version number | (Optional) Defines the Network Time Protocol (NTP) version number (1 to 3). |
key keyid | (Optional) Defines the authentication key when sending packets to this peer. |
source interface | (Optional) Names the interface from which to pick the IP source address. |
prefer | (Optional) Makes this peer the preferred peer that provides synchronization. |
No peers are configured by default. If a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IP address is taken from the outgoing interface.
Global configuration
Use this command if you want to allow this communication server to synchronize with the peer, or vice versa. Using the prefer keyword will reduce switching back and forth between peers.
If you are using the default version of 3 and NTP synchronization does not occur, try using NTP version number 2. Many NTP servers on the Internet run version 2.
In the following example, the communication server is configured to allow its system clock to be synchronized with the clock of the peer (or vice versa) at IP address 131.108.22.33 using NTP version 2. The source IP address will be the address of Ethernet interface 0.
ntp peer 131.108.22.33 version 2 source Ethernet 0
ntp authentication-key
ntp server
ntp source
To allow the communication server's system clock to be synchronized by a time server, use the ntp server global configuration command. To disable this capability, use the no form of this command.
ntp server ip-address [version number] [key keyid] [source interface] [prefer]
ip-address | IP address of the time server providing the clock synchronization. |
version number | (Optional) Defines the Network Time Protocol (NTP) version number (1 to 3). |
key keyid | (Optional) Defines the authentication key to use when sending packets to this peer. |
source interface | (Optional) Identifies the interface from which to pick the IP source address. |
prefer | (Optional) Makes this server the preferred server that provides synchronization. |
No peers are configured by default. If a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IP address is taken from the outgoing interface.
Global configuration
Use this command if you want to allow this communication server to synchronize with the specified server. The server will not synchronize to this communication server.
Using the prefer keyword will reduce switching back and forth between servers.
If you are using the default version of 3 and NTP synchronization does not occur, try using NTP version number 2. Many NTP servers on the Internet run version 2.
In the following example, the communication server is configured to allow its system clock to be synchronized with the clock of the peer at IP address 128.108.22.44 using NTP version 2:
ntp server 128.108.22.44 version 2
ntp authentication-key
ntp peer
ntp source
To use a particular source address in Network Time Protocol (NTP) packets, use the ntp source global configuration command. Use the no form of this command to remove the specified source address.
ntp source interface
interface | Any valid system interface name |
Source address is determined by the outgoing interface.
Global configuration
Use this command when you want to use a particular source IP address for all NTP packets. The address is taken from the named interface. This command is useful if the address on an interface cannot be used as the destination for reply packets. If the source keyword is present on an ntp server or ntp peer command, that value overrides the global value.
In the following example, the communication server is configured to use the IP address of Ethernet interface 0 as the source address of all outgoing NTP packets:
ntp source ethernet 0
ntp peer
ntp server
If you want to authenticate the identity of a system to which Network Time Protocol (NTP) will synchronize, use the ntp trusted-key global configuration command. Use the no form of this command to disable authentication of the identity of the system.
ntp trusted-key key-number
key-number | Key number of authentication key to be trusted |
Disabled
Global configuration
If authentication is enabled, use this command to define one or more key numbers (corresponding to the keys defined with the ntp authentication-key command) that a peer NTP system must provide in its NTP packets, in order for this system to synchronize to it. This provides protection against accidentally synchronizing the system to a system that is not trusted, since the other system must know the correct authentication key.
In the following example, the system is configured to synchronize only to systems providing authentication key 42 in its NTP packets:
ntp authenticate
ntp authentication-key 42 md5 aNiceKey
ntp trusted-key 42
ntp authenticate
ntp authentication-key
Use the ping (packet internet groper) user EXEC command to diagnose basic network connectivity on IP and Novell IPX networks.
ping [protocol] {host | address}
protocol | (Optional) Protocol keyword, either ip or novell |
host | Host name of system to ping |
address | Address of system to ping |
User EXEC
The user-level ping feature provides a basic ping facility for users who do not have system privileges. This feature allows the communication server to perform the simple default ping functionality for a number of protocols. Only the nonverbose form of the ping command is supported for user-level pings. Unlike the privileged-level ping command, the values for the number of ping packets sent, the datagram size, and the timeout cannot be adjusted.
If the system cannot map an address for a host name, it will return an "%Unrecognized host or address" error message.
To abort a ping session, type the escape sequence (by default, Ctrl-^ X, which is done by simultaneously pressing the Ctrl, Shift, and 6 keys, letting go, then pressing the X key).
Table 5-9 describes the test characters that the ping facility sends.
| Char | Meaning |
|---|---|
! | Each exclamation point indicates receipt of a reply. |
. | Each period indicates the network server timed out while waiting for a reply. |
U | A destination unreachable error PDU was received. |
C | A congestion experienced packet was received. |
I | User interrupted test. |
? | Unknown packet type. |
& | Packet lifetime exceeded. |
The following display shows sample ping output when you ping the IP host named donald:
cs> ping donald
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.31.7.27, timeout is 2 seconds:
!!!!!
Success rate is 100 percent, round-trip min/avg/max = 1/3/4 ms
Table 5-10 describes the default ping fields shown in the display.
| Field | Description |
|---|---|
Sending 5, 100-byte ICMP echos to | Indicates the number of ping packets sent to the specified host name, the datagram size, and the timeout value. |
!!!!! | Each exclamation point (!) indicates receipt of a reply. A period (.) indicates the network server timed out while waiting for a reply. Other characters might appear in the ping output display, depending on the protocol type. |
Success rate is 100 percent | Percentage of packets successfully echoed back to the communication server. Anything less than 80 percent is usually considered problematic. |
round-trip min/avg/max = 1/3/4 ms | Round-trip travel time intervals for the protocol echo packets, including minimum/average/maximum (in milliseconds). |
ping (privileged)
Use the ping (packet internet groper) privileged EXEC command to diagnose basic network connectivity on IP and Novell IPX networks.
ping [protocol] {host | address}
protocol | (Optional) Protocol keyword, either ip or novell |
host | Host name of system to ping |
address | Address of system to ping |
Privileged EXEC
The ping program sends an echo request packet to an address, then awaits a reply. Ping output can help you evaluate path-to-host reliability, delays over the path, and whether the host can be reached or is functioning.
Depending upon the protocol type, You can adjust values for the number of ping packets to be sent, the datagram size, the timeout interval, additional command to include, and the sizes of the echo packets being sent.
After you enter the ping command in privileged mode, the system prompts for one of the following keywords: ip or ipx. The default protocol is IP.
If you enter a host name or address on the same line as the ping command, the default action is taken as appropriate for the protocol type of that name or address.
To abort a ping session, type the escape sequence (by default, Ctrl-^ X, which is done by simultaneously pressing the Ctrl, Shift, and 6 keys, letting go, then pressing the X key).
Table 5-11 describes the test characters that the ping facility sends.
| Char | Meaning |
|---|---|
! | Each exclamation point indicates receipt of a reply. |
. | Each period indicates the network server timed out while waiting for a reply. |
U | A destination unreachable error PDU was received. |
C | A congestion experienced packet was received. |
I | User interrupted test. |
? | Unknown packet type. |
& | Packet lifetime exceeded. |
While the precise dialog varies somewhat from protocol to protocol, all are similar to the ping session using default values shown in the following display:
cs# ping
Protocol [ip]:
Target IP address: 192.31.7.27
Repeat count [5]:
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.31.7.27, timeout is 2 seconds:
!!!!!
Success rate is 100 percent, round-trip min/avg/max = 1/2/4 ms
Table 5-12 describes the default ping fields shown in the display.
| Field | Description |
|---|---|
Protocol [ip]: | Prompts for a supported protocol. Enter ip or novell. Default: ip. |
Target IP address: | Prompts for the IP address or host name of the destination node you plan to ping. If you have specified a supported protocol other than IP, enter an appropriate address for that protocol here. Default: none. |
Repeat count [5]: | Number of ping packets that will be sent to the destination address. Default: 5. |
Datagram size [100]: | Size of the ping packet (in bytes). Default: 100 bytes. |
Timeout in seconds [2]: | Timeout interval. Default: 2 (seconds). |
Extended commands [n]: | Specifies whether or not a series of additional commands appears. Many of the following displays and tables show and describe these commands. |
Sweep range of sizes [n]: | Allows you to vary the sizes of the echo packets being sent. This capability is useful for determining the minimum sizes of the MTUs configured on the nodes along the path to the destination address. Packet fragmentation contributing to performance problems can then be reduced. |
!!!!! | Each exclamation point (!) indicates receipt of a reply. A period (.) indicates the network server timed out while waiting for a reply. Other characters might appear in the ping output display, depending on the protocol type. |
Success rate is 100 percent | Percentage of packets successfully echoed back to the communication server. Anything less than 80 percent is usually considered problematic. |
round-trip min/avg/max = 1/2/4 ms | Round-trip travel time intervals for the protocol echo packets, including minimum/average/maximum (in milliseconds). |
ping (user)
To enable Challenge Handshake Authentication Protocol (CHAP) or Password Authentication Protocol (PAP), and to enable an AAA authentication method on an interface, use the ppp authentication interface configuration command. Use the no form of the command to disable this authentication.
ppp authentication {chap | pap} [if-needed] [list-name]
chap | Enable CHAP on a serial interface. |
pap | Enable PAP on a serial interface. |
if-needed | (Optional) Used with TACACS and XTACACS. Do not perform CHAP or PAP authentication if user has already provided authentication. This option is available only on asynchronous interfaces. |
list-name | (Optional) Used with AAA/TACACS+. Specify the name of a list of AAA methods of authentication to use. If no listname is specified, the system will use the default. Lists and default are created using the aaa authentication ppp command. |
PPP authentication is not enabled.
Interface configuration
Once you have enabled CHAP or PAP, the local communication server requires a password from remote devices. If the remote device does not support CHAP or PAP, no traffic will be passed to that device.
If you are using autoselect on a tty line, you will probably want to use the ppp authentication command to turn on PPP authentication for the corresponding interface.
When you specify the if-needed option, PPP authentication is not required when the user has already provided authentication. This option is useful in conjunction to the autoselect command, but cannot be used with AAA/TACACS+.
The list-name keyword can only be used when AAA/TACACS+ is initialized and cannot be used with the if-needed argument.
| Caution If you use a list-name that was not configured with the aaa authentication ppp command, you will disable PPP on this interface. |
The following example enables CHAP on asynchronous interface 4:
interface async 4
encapsulation ppp
ppp authentication chap
A dagger (†) indicates that the command is documented in another chapter.
aaa authentication ppp†
aaa new-model
autoselect†
encapsulation ppp†
ppp use-tacacs†
username†
To enable TACACS for PPP authentication, use the ppp use-tacacs interface configuration command. Use the no form of this command to disable TACACS for PPP authentication.
ppp use-tacacs [single-line]
single-line | (Optional) Accept the username and password in the username field. This option applies only when using CHAP authentication. |
TACACS is not used for PPP authentication.
Interface configuration
This is a per-interface command. Use this command only when you have set up an extended TACACS server. This command requires the new extended TACACS server.
When CHAP authentication is being used, the ppp use-tacacs command with the single-line option specifies that if a username and password are specified in the username, separated by an asterisk (*), then a standard tacacs login query is performed using that username and password. If the username does not contain an asterisk, then normal CHAP authentication is performed using TACACS.
This feature is useful when integrating TACACS with other authentication systems that require a clear-text version of the user's password. Such systems include one-time password systems, token card systems, and others.
| Caution Normal CHAP authentications prevent the clear-text password from being transmitted over the link. When you use the single-line option, passwords will cross the link in the clear. |
If the username and password are contained in the CHAP password, then the CHAP secret is not used by the Cisco system. Because most PPP clients will require that a secret be specified, you can use any arbitrary string; the Cisco system will ignore it.
In the following example, asynchronous serial interface 1 is configured to use TACACS for CHAP authentication:
interface async 1
ppp authentication chap
ppp use-tacacs
In the following example, asynchronous serial interface 1 is configured to use TACACS for PAP authentication:
interface async 1
ppp authentication pap
ppp use-tacacs
A dagger (†) indicates that the command is documented in another chapter.
ppp authentication chap†
ppp authentication pap†
tacacs-server extended †
tacacs-server host†
To assign the specified priority list to an interface, use the priority-group interface configuration command. Use the no form of this command to remove the specified priority-group assignment.
priority-group list
list | Priority list number assigned to the interface |
None
Interface configuration
Only one list can be assigned per interface. Priority output queueing provides a mechanism to prioritize packets transmitted on an interface.
The following example causes packets on serial interface 0 to be classified by priority list 1:
interface serial 0
priority-group 1
priority-list
priority-list interface
priority-list queue-limit
priority-list stun
To assign a priority queue for those packets that do not match any other rule in the priority list, use the priority-list default global configuration command. Use the no form of this command to return to the default or assign normal as the default.
priority-list list-number default {high | medium | normal | low}
list-number | Arbitrary integer between 1 and 10 that identifies the priority list selected by the user |
high | medium | normal | low | Priority queue level |
The normal queue is assumed if you use the no form of the command.
Global configuration
The following example sets the priority queue for those packets that do not match any other rule in the priority list to a low priority:
priority-list 1 default low
priority-group
show queueing
To establish queuing priorities on packets entering from a given interface, use the priority-list interface global configuration command. Use the no priority-list command with the appropriate arguments to remove an entry from the list.
priority-list list-number interface interface-type interface-number {high | medium |
list-number | Arbitrary integer between 1 and 10 that identifies the priority list selected by the user |
interface-type | Name of the interface |
interface-number | Number of the specified interface |
high | medium | normal | low | Priority queue level |
No queuing priorities are established.
Global configuration
The following example sets any packet type entering on Ethernet interface 0 to a medium priority:
priority-list 3 interface ethernet 0 medium
priority-group
show queueing
To establish queuing priorities based upon the protocol type, use the priority-list protocol global configuration command. Use the no form of this command with the appropriate list number to remove an entry from the list.
priority-list list-number protocol protocol-name {high | medium | normal | low}
list-number | Arbitrary integer between 1 and 10 that identifies the priority list selected by the user. |
protocol-name | Specifies the protocol type: arp, compressedtcp, ip, ipx, pad, and x25. |
high | medium | normal | low | Priority queue level. |
queue-keyword keyword-value | Possible keywords are gt, lt, list, tcp, and udp. See Table 5-13. |
No queuing priorities are established.
Global configuration
When using multiple rules for a single protocol, remember that the system reads the priority settings in order of appearance. When classifying a packet, the system searches the list of rules specified by priority-list commands for a matching protocol type. When a match is found, the packet is assigned to the appropriate queue. The list is searched in the order it is specified, and the first matching rule terminates the search.
Use Table 5-13, Table 5-14, and Table 5-15 to configure the queuing priorities for your system.
| Option | Description |
|---|---|
gt byte-count | Specifies a greater-than count. The priority level assigned goes into effect when a packet exceeds the value entered for the argument byte-count. The size of the packet must also include additional bytes due to MAC encapsulation on the outgoing interface. |
lt byte-count | Specifies a less-than count. The priority level assigned goes into effect when a packet size is less than the value entered for byte-count. The size of the packet must also include additional bytes due to MAC encapsulation on the outgoing interface. |
list list-number | Assigns traffic priorities according to a specified list when used with IP or IPX. The list-number argument is the access list number as specified by the access-list global configuration command for the specified protocol-name. |
tcp port | Assigns the priority level defined to TCP segments originating from or destined to a specified port (for use with the IP protocol only). Table 5-14 lists common TCP services and their port numbers. |
udp port | Assigns the priority level defined to UDP packets originating from or destined to the specified port (for use with the IP protocol only). Table 5-15 lists common UDP services and their port numbers. |
| Service | Port |
|---|---|
Telnet | 23 |
SMTP | 25 |
| Service | Port |
|---|---|
TFTP | 69 |
NFS | 2049 |
SNMP | 161 |
RPC | 111 |
DNS | 53 |
Use the no priority-list global configuration command followed by the appropriate list-number argument and the protocol keyword to remove a priority list entry assigned by protocol type.
The following example assigns a high-priority level to traffic that matches IP access list 10:
priority-list 1 protocol ip high list 10
The following example assigns a medium-priority level to Telnet packets:
priority-list 4 protocol ip medium tcp 23
The following example assigns a medium-priority level to UDP Domain Name Service packets:
priority-list 4 protocol ip medium udp 53
The following example assigns a high-priority level to traffic that matches Ethernet type code access list 201:
priority-list 1 protocol bridge high list 201
priority-group
show queueing
To specify the maximum number of packets that can be waiting in each of the priority queues, use the priority-list queue-limit global configuration command. Use the no form of this command to select the normal queue.
priority-list list-number queue-limit high-limit medium-limit normal-limit low-limit
list-number | Arbitrary integer between 1 and 10 that identifies the priority list selected by the user. |
high-limit medium-limit | Priority queue maximum length. A value of 0 for any of the four arguments means that the queue can be of unlimited size for that particular queue. |
The default queue limit arguments are listed in Table 5-16.
| Priority Queue Argument | Packet Limits |
|---|---|
high-limit | 20 |
medium-limit | 40 |
normal-limit | 60 |
low-limit | 80 |
Global configuration
If a priority queue overflows, excess packets are discarded and quench messages can be sent, if appropriate, for the protocol.
The following example sets the maximum packets in the priority queue to 10:
priority-list 2 queue-limit 10 40 60 80
priority-group
show queueing
mode | Configuration mode. See Table 5-6 in the description of the alias command for a list of acceptable options. |
level | Privilege level to be associated with the specified command. You can specify up to sixteen privilege levels, using numbers 0 through 15. |
command | Command to which privilege level is associated. |
Level 15 is the level of access permitted by the enable password.
Level 1 is normal EXEC-mode user privileges.
Global configuration
Table 5-6 in the description of the alias command shows the acceptable options for the mode argument in the privilege level global configuration command.
The password for the privilege level defined using the privilege level global configuration mode is configured using the enable password command.
Level 0 can be used to specify a more-limited subset of commands for specific users or lines. For example, you can allow user "guest" to only use the show users and exit commands.
In the following example, the configure command in global configuration mode is assigned a privilege level of 14. Only users who know the level 14 password will be able to use the configure command.
privilege exec level 14 configure
enable password level 14 pswd14
enable password
privilege level (line)
To set the default privilege level for a line, use the privilege level line configuration command. Use the no privilege level command to restore the default user privilege level to the line.
privilege level level
level | Privilege level to be associated with the specified line. |
Level 15 is the level of access permitted by the enable password.
Level 1 is normal EXEC-mode user privileges.
Line configuration
The privilege level that is set using this command can be overridden by a user logging into the line and enabling a different privilege level. The user can lower the privilege level by using the disable command. If they know the password to a higher privilege level, they can use that password to enable the higher privilege level.
Level 0 can be used to specify a more limited subset of commands for specific users or lines. For example, you can allow user "guest" to only use the show users and exit commands.
You might specify a high level of privilege for your console line if you are able to restrict who uses that line.
In the following example, the auxiliary line is configured for privilege level 5. Anyone who is using the auxiliary line will have privilege level 5 by default.
line aux 0
privilege level 5
enable password
privilege level (global)
To customize the communication server prompt, use the prompt global configuration command. To revert to the default communication server prompt, use the no form of this command.
prompt string
string | Communication server prompt. It can consist of all printing characters and the escape sequences listed in Table 5-17 in the Usage Guidelines section below. |
The default communication server prompt is either cs or the communication server name defined with the hostname global configuration command, followed by an angle bracket (>) for EXEC mode or a pound sign (#) for privileged EXEC mode.
Global configuration
You can include escape sequences when specifying the communication server prompt. All escape sequences are preceded by a percent sign (%). Table 5-17 lists the valid escape sequences.
| Escape Sequence | Interpretation |
|---|---|
%h | Communication server's host name. This is either cs or the name defined with the hostname global configuration command. |
%n | Physical terminal line (TTY) number of the EXEC user. |
%p | Prompt character itself. It is either an angle bracket (>) for EXEC mode or a pound sign (#) for privileged EXEC mode. |
%s | Space. |
%t | Tab. |
%% | Percent sign (%) |
Specifying the command prompt %h has the same effect as issuing the no prompt command.
The following example changes the EXEC prompt to include the TTY number, followed by the communication server name and a space:
prompt TTY%n@%h%s%p
The following are examples of user and privileged EXEC prompts that result from the previous command:
TTY17@cs >
TTY17Scs #
hostname
To assign a priority queue for those packets that do not match any other rule in the queue list, use the queue-list default global configuration command. To restore the default value, use the
no form of this command.
list-number | Number of the queue list. An integer from 1 to 10. |
queue-number | Number of the queue. An integer from 1 to 10. |
Queue number 1
Global configuration
Queue number 0 is a system queue. It is emptied before any of the other queues are processed. The system enqueues high-priority packets, such as keepalives, to this queue.
In the following example, the default queue for list 10 is set to queue number 2:
queue-list 10 default 2
custom-queue-list
show queueing
To establish queuing priorities on packets entering on an interface, use the queue-list interface global configuration command. To remove an entry from the list, use the no form of this command.
queue-list list-number interface interface-type interface-number queue-number
list-number | Number of the queue list. An integer from 1 to 10. |
interface-type | Required argument that specifies the name of the interface. |
interface-number | Number of the specified interface. |
queue-number | Number of the queue. An integer from 1 to 10. |
No queuing priorities are established.
Global configuration
In the following example, queue list 4 established queuing priorities for packets entering on interface tunnel 3. The queue number assigned is 10.
queue-list 4 interface tunnel 3 10
custom-queue-list
show queueing
To establish queuing priority based upon the protocol type, use the queue-list protocol global configuration command. Use the no form of this command with the appropriate list number to remove an entry from the list.
queue-list list-number protocol protocol-name queue-number queue-keyword keyword-value
list-number | Number of the queue list. An integer from 1 to 10. |
protocol-name | Required argument that specifies the protocol type: arp, compressedtcp, ip, ipx, pad, and x25. |
queue-number | Number of the queue. An integer from 1 to 10. |
queue-keyword keyword-value | Possible keywords are gt, lt, list, tcp, and udp. See Table 5-13. |
No queuing priorities are established.
Global configuration
When classifying a packet, the system searches the list of rules specified by queue-list commands for a matching protocol type. When a match is found, the packet is assigned to the appropriate queue. The list is searched in the order it is specified, and the first matching rule terminates the search.
Use Table 5-13, Table 5-14, and Table 5-15 from the priority-list protocol command to configure custom queuing for your system.
The following example assigns traffic that matches IP access list 10 to queue number 1:
queue-list 1 protocol ip 1 list 10
The following example assigns Telnet packets to queue number 2:
queue-list 4 protocol ip 2 tcp 23
The following example assigns UDP Domain Name System packets to queue number 2:
queue-list 4 protocol ip 2 udp 53
The following example assigns traffic that matches Ethernet type code access list 201 to queue number 1:
queue-list 1 protocol bridge 1 list 201
custom-queue-list
show queueing
To designate the byte size allowed per queue, use the queue-list queue byte-count global configuration command. To return the byte size to the default value, use the no form of this command.
queue-list list-number queue queue-number byte-count byte-count-number
| list-number | Number of the queue list. An integer from 1 to 10. |
|---|---|
queue-number | Number of the queue. An integer from 1 to 10. |
byte-count-number | Specifies the lower boundary on how many bytes the system allows to be delivered from a given queue during a particular cycle. |
1500 bytes
Global configuration
In the following example, queue list 9 establishes the byte-count as 1400 for queue number 10:
queue-list 9 queue 10 byte-count 1400
custom-queue-list
show queueing
To designate the queue length limit for a queue, use the queue-list queue limit global configuration command. To return the queue length to the default value, use the no form of this command.
queue-list list-number queue queue-number limit limit-number
| list-number | Number of the queue list. An integer from 1 to 10. |
|---|---|
queue-number | Number of the queue. An integer from 1 to 10. |
limit-number | Maximum number of packets which can be enqueued at any time. |
20 entries
Global configuration
In the following example, the queue length of queue 10 is increased to 40:
queue-list 5 queue 10 limit 40
custom-queue-list
show queueing
To control the maximum amount of time that can elapse without running the lowest-priority system processes, use the scheduler-interval global configuration command. Use the no form of this command to restore the default.
scheduler-interval milliseconds
milliseconds | Integer that specifies the interval, in milliseconds. The minimum interval that you can specify is 500 milliseconds; there is no maximum value. |
500 milliseconds
Global configuration
The normal operation of the network server allows the switching operations to use as much of the central processor as is required. If the network is running unusually heavy loads that do not allow the processor the time to handle the routing protocols, give priority to the system process scheduler. High-priority operations are allowed to use as much of the central processor as needed.
The following example changes the low-priority process schedule to an interval of 750 milliseconds:
scheduler-interval 750
To specify that line numbers be displayed and interpreted as decimal numbers rather than octal numbers, use the service decimal-tty global configuration command. Use the no form of this command to restore the default.
service decimal-ttyThis command has no arguments or keywords.
Octal line numbers on the ASM-CS; decimal numbers on the 500-CS and Cisco 2500 Series.
Global configuration
The following example shows how to display decimal rather than octal line numbers:
service decimal-tty
To delay the startup of the EXEC on noisy lines, use the service exec-wait global configuration command. Use the no form of this command to disable this feature.
service exec-waitThis command has no arguments or keywords.
Disabled
Global configuration
This command delays startup of the EXEC until the line has been idle (no traffic seen) for 3 seconds. The default is to enable the line immediately on modem activation.
This command is useful on noisy modem lines or when a modem attached to the line is configured to ignore MNP or V.42 negotiations, and MNP or V.42 modems may be dialing in. In these cases, noise or MNP/V.42 packets might be interpreted as usernames and passwords, causing authentication failure before the user gets a chance to type a username/password. The command is not useful on nonmodem lines or lines without some kind of login configured.
The following example delays the startup of the EXEC:
service exec-wait
To allow Finger protocol requests (defined in RFC 742) to be made of the network server, use the service finger global configuration command. This service is equivalent to issuing a remote show users command. The no service finger command removes this service.
service fingerThis command has no arguments or keywords.
Enabled
Global configuration
The following is an example of how to disable the Finger protocol:
no service finger
To enable the Nagle congestion control algorithm, use the service nagle global configuration command. Use the no form of this command to disable this feature.
service nagleThis command has no arguments or keywords.
Disabled
Global configuration
When using a standard TCP implementation to send keystrokes between machines, TCP tends to send one packet for each keystroke typed. On larger networks, many small packets use up bandwidth and contribute to congestion.
John Nagle's algorithm (RFC 896) helps alleviate the small-packet problem in TCP. In general, it works this way: The first character typed after connection establishment is sent in a single packet, but TCP holds any additional characters typed until the receiver acknowledges the previous packet. Then the second, larger packet is sent, and additional typed characters are saved until the acknowledgment comes back. The effect is to accumulate characters into larger chunks, and pace them out to the network at a rate matching the round-trip time of the given connection. This method is usually a good for all TCP-based traffic. However, do not use the service nagle command if you have XRemote users on X Window sessions.
The following example enables the Nagle algorithm on the communication server:
service nagle
This command has no arguments or keywords.
No encryption
Global configuration
The actual encryption process occurs when the current configuration is written or when a password is configured. Password encryption can be applied to both the privileged command password and to console and virtual terminal line access passwords.
When password encryption is enabled, the encrypted form of the passwords is displayed when a show configuration command is entered.
The following example causes password encryption to take place:
service password-encryption
in | Generates keepalives on incoming connections (initiated by remote host). |
out | Generates keepalives on outgoing connections (initiated by a user). |
Disabled
Global configuration
The following example generates keepalives on incoming TCP connections:
service tcp-keepalives in
To set the TCP window to zero (0) when the Telnet connection is idle, use the service telnet-zero-idle global configuration command. Use the no form of this command to disable this feature.
service telnet-zero-idleThis command has no arguments or keywords.
Disabled
Global configuration
Normally, data sent to noncurrent Telnet connections is accepted and discarded. When service telnet-zero-idle is enabled, if a session is suspended (that is, some other connection is made active or the EXEC is sitting in command mode), the TCP window is set to zero. This action prevents the remote host from sending any more data until the connection is resumed. Use this command when it is important that all messages sent by the host be seen by the users and the users are likely to use multiple sessions.
Do not use this command if your host will eventually time out and log out a TCP user whose window is zero.
The following example sets the TCP window to zero when the Telnet connection is idle:
service telnet-zero-idle
resume
To configure the system to timestamp debugging or logging messages, use one of the service timestamps global configuration commands. Use the no form of this command to disable this service.
service timestamps [type uptime]
type | (Optional) Type of message to timestamp: debug or log. |
uptime | (Optional) Timestamp with time since the system was rebooted. |
datetime | Timestamp with the date and time. |
msec | (Optional) Timestamp includes milliseconds with the date and time. |
localtime | (Optional) Timestamp relative to the local time zone. |
show-timezone | (Optional) Timestamp includes the time-zone name. |
No timestamping.
If service timestamps is specified with no arguments or keywords, the default is service timestamps debug uptime.
The default for service timestamps type datetime is to format the time in UTC, with no milliseconds and no time-zone name.
The command no service timestamps with no arguments or keywords disables timestamps for both debugging and logging messages.
Global configuration
Timestamps can be added to either debugging or logging messages independently. The uptime form of the command adds timestamps in the format HHHH:MM:SS, indicating the time since the system was rebooted. The datetime form of the command adds timestamps in the format
MMM DD HH:MM:SS, indicating the date and time according to the system clock. If the system clock has not been set, the date and time are preceded by an asterisk (*) to indicate that the date and time are probably not correct.
The following example enables timestamps on debugging messages, showing the time since reboot:
service timestamps debug uptime
The following example enables timestamps on logging messages, showing the current time and date relative to the local time zone, with the time zone name included:
service timestamps log datetime localtime show-timezone
clock set
debug (Refer to the Debug Command Reference publication.)
ntp
To display all alias commands, or the alias commands in a specified mode, use the show aliases privileged EXEC command.
show aliases [mode]
mode | (Optional) Command mode. See Table 5-6 in the description of the alias command for acceptable options for the mode argument. |
Table 5-6 shows the options for the optional mode argument in the show aliases privileged EXEC command.
Privileged EXEC
All of the modes listed in Table 5-6 have their own prompts, except for the null interface mode. For example, the prompt for interface configuration mode is cs(config-if).
The following is sample output from the show aliases exec commands. The aliases configured for commands in EXEC mode are displayed.
cs# show aliases exec
Exec mode aliases:
h help
lo logout
p ping
r resume
s show
w where
alias
Use the show buffers EXEC command to display statistics for the buffer pools on the network server.
The network server has one pool of queuing elements and five pools of packet buffers of different sizes. For each pool, the network server keeps counts of the number of buffers outstanding, the number of buffers in the free list, and the maximum number of buffers allowed in the free list.
show buffers [type number]] | all]
type number | (Optional) Causes a search of all buffers that have been associated with that interface type and number for longer than one minute. The contents of these buffers are printed to the screen. This option is useful in diagnosing problems where the input queue count on an interface is consistently nonzero. |
all | (Optional) Displays all public and interface pool information. |
interface | (Optional) Displays all interface pool information. If the specified interface type and number has its own buffer pool, displays information for that pool. |
type number | (Optional) Displays interface pool information for the specified interface type and number if the specified interface type and number has its own buffer pool. Value of type can be ethernet, serial, or tokenring. |
alloc | (Optional) Displays a brief listing of all allocated buffers. When alloc is specified after interface type number, displays a brief listing of buffers allocated for that interface. |
dump | (Optional) Dumps all allocated buffers. This keyword must be used with the alloc keyword, not by itself. When alloc dump is specified after interface type number, dumps buffers allocated for that interface. |
EXEC
The following is sample output from the show buffers command with no optional arguments; showing all buffer pool and interface buffer pool information:
CS# show buffers
Buffer elements:
421 in free list (500 max allowed)
409 hits, 0 misses, 0 created
Public buffer pools:
Small buffers, 104 bytes (total 50, permanent 50):
50 in free list (20 min, 150 max allowed)
277 hits, 0 misses, 0 trims, 0 created
Middle buffers, 600 bytes (total 25, permanent 25):
24 in free list (10 min, 75 max allowed)
19 hits, 0 misses, 0 trims, 0 created
Big buffers, 1524 bytes (total 50, permanent 50):
50 in free list (5 min, 40 max allowed)
4 hits, 0 misses, 0 trims, 0 created
Large buffers, 5024 bytes (total 0, permanent 0):
0 in free list (0 min, 10 max allowed)
0 hits, 0 misses, 0 trims, 0 created
Huge buffers, 18024 bytes (total 0, permanent 0):
0 in free list (0 min, 4 max allowed)
0 hits, 0 misses, 0 trims, 0 created
Interface buffer pools:
Fddi buffers, 5024 bytes (total 256, permanent 256):
0 in free list (0 min, 256 max allowed)
256 hits, 0 misses
256 max cache size, 110 in cache
14 buffer threshold, 0 threshold transitions
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 misses
16 max cache size, 16 in cache
Ethernet1 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 misses
16 max cache size, 16 in cache
Serial0 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 misses
16 max cache size, 16 in cache
Serial1 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 misses
16 max cache size, 16 in cache
0 failures (0 no memory)
Table 5-18 describes significant fields shown in the display.
| Field | Description |
|---|---|
Buffer elements | Buffer elements are small structures used as placeholders for buffers in internal operating system queues. Buffer elements are used when a buffer may need to be on more than one queue. |
— in free list (— max allowed) | Maximum number of buffers that are available for allocation. |
hits | Count of successful attempts to allocate a buffer when needed. |
misses | Count of buffer allocation attempts that resulted in growing the buffer pool in order to allocate a buffer. |
created | Count of new buffers created to satisfy buffer allocation attempts when the available buffers in the pool have already been allocated. |
Public buffer pools |
|
Small buffers | Blocks of memory used to hold network packets. The sizes of these buffers can vary as follows: small, middle, big, large and huge. |
bytes | Size of this type of buffer. |
(total , permanent ) | Total number of this type of buffer, and the number of these buffers that are permanent. |
trims | Count of buffers released to the system because they were not being used. This field is displayed only for dynamic buffer pools, not interface buffer pools, which are static. |
created | Count of new buffers created in response to misses. This field is displayed only for dynamic buffer pools, not interface buffer pools, which are static. |
failures | Total number of allocation requests that have failed because no buffer was available for allocation; the datagram was lost. Such failures normally occur at interrupt level. |
(no memory) | Number of failures because no memory was available to create a new buffer. |
Interface buffer pools | Static. |
The following is sample output from the show buffers command when an interface type and number are specified:
CS# show buffers ethernet 0
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 misses
16 max cache size, 16 in cache
The following is sample output from the show buffers command when all is specified:
CS# show buffers all
Buffer elements:
Free Max Hit Miss Creat
Free ed
--------------------------------------------------------------------------------
427 500 17553 0 0
Public buffer pools:
Pool Buffer Total Perm Free Min Max Hit Miss Trim Creat Need Ex-
Name Size Free Free ed tra
--------------------------------------------------------------------------------
Small 104 50 50 50 20 150 14141 0 0 0
Middle 600 25 25 25 10 75 36 0 0 0
Big 1524 50 50 50 5 40 18 0 0 0
Large 5024 0 0 0 0 10 0 0 0 0
Huge 18024 0 0 0 0 4 0 0 0 0
Interface buffer pools:
Pool Buffer Total Perm Free Min Max Hit Fall Cache Cache Need Ex-
Name Size Free Free back Max Free tra
--------------------------------------------------------------------------------
Serial0 1524 96 96 31 0 96 65 0 32 32
Serial1 1524 96 96 31 0 96 65 0 32 32
Ethernet0 1524 96 96 32 0 96 64 0 32 32
0 failures (0 no memory)
The following is sample output from the show buffers command when alloc is specified:
CS# show buffers alloc
Buffer elements:
Free Max Hit Miss Creat
Free ed
--------------------------------------------------------------------------------
427 500 18589 0 0
Public buffer pools:
Pool Buffer Total Perm Free Min Max Hit Miss Trim Creat Need Ex-
Name Size Free Free ed tra
--------------------------------------------------------------------------------
Small 104 50 50 50 20 150 14982 0 0 0
Middle 600 25 25 25 10 75 36 0 0 0
Big 1524 50 50 50 5 40 18 0 0 0
Large 5024 0 0 0 0 10 0 0 0 0
Huge 18024 0 0 0 0 4 0 0 0 0
0 failures (0 no memory)
Address PakAddr Data Off Data Pool Ref Link Enc Flags Output Input
Area set Size Cnt Type Type (Hex) Idb Idb
--------------------------------------------------------------------------------
604A8C20 604A8C40 40007550 84 0 Seria 1 0 0 0
604B6A80 604B6AA0 40007BD4 84 0 Seria 1 0 0 0
.
To display global CDP information, including timer and hold-time information, use the show cdp privileged EXEC command.
show cdpThis command has no arguments or keywords.
Privileged EXEC
The following is sample output from the show cdp command. Global CDP timer and hold-time parameters are set to the defaults of 60 and 180 seconds, respectively.
cs# show cdp
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime value of 180 seconds
cdp holdtime
cdp timer
show cdp entry
show cdp neighbors
To display information about a neighbor device listed in the CDP table, use the show cdp entry privileged EXEC command.
show cdp entry entry-name [protocol | version]
entry-name | Name of neighbor about which you want information. |
protocol | (Optional) Limits the display to information about the protocols enabled on a device. |
version | (Optional) Limits the display to information about the version of software running on the device. |
Privileged EXEC
The following is sample output from the show cdp entry command with no limits. Information about the neighbor device.cisco.com is displayed, including device ID, address and protocol, platform, interface, hold-time, and version.
cs# show cdp entry device.cisco.com
Device ID: device.cisco.com
Entry address(es):
IP address: 198.92.68.18
CLNS address: 490001.1111.1111.1111.00
DECnet address: 10.1
Platform: AGS, Capabilities: Router Trans-Bridge
Interface: Ethernet0, Port ID (outgoing port): Ethernet0
Holdtime : 155 sec
Version :
GS Software (GS3), Experimental Version 10.2(10302) [asmith 161]
Copyright (c) 1986-1994 by cisco Systems, Inc.
Compiled Mon 07-Nov-94 14:34
The following is sample output from the show cdp entry privilege command. Only information about the protocols enabled on neon-cisco.com is displayed.
cs# show cdp entry device.cisco.com protocol
Protocol information for device.cisco.com :
IP address: 198.92.68.18
CLNS address: 490001.1111.1111.1111.00
DECnet address: 10.1
The following is sample output from the show cdp entry version command. Only information about the version of software running on device.cisco.com is displayed.
cs# show cdp entry device.cisco.com version
Version information for device.cisco.com :
GS Software (GS3), Experimental Version 10.2(10302) [asmith 161]
Copyright (c) 1986-1994 by cisco Systems, Inc.
Compiled Mon 07-Nov-94 14:34
show cdp neighbors
To display information about the interfaces on which CDP is enabled, use the show cdp interface privileged EXEC command.
show cdp interface [type number]
type | (Optional) Type of interface about which you want information. |
number | (Optional) Number of the interface about which you want information. |
Privileged EXEC
The following is sample output from the show cdp interface command. Status information and information about CDP timer and hold-time settings is displayed for all interfaces on which CDP is enabled.
cs# show cdp interface
Serial0 is up, line protocol is up, encapsulation is SMDS
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
Ethernet0 is up, line protocol is up, encapsulation is ARPA
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
The following is sample output from the show cdp interface command with an interface specified. Status information and information about CDP timer and hold-time settings is displayed for Ethernet interface 0 only.
cs# show cdp interface ethernet 0
Ethernet0 is up, line protocol is up, encapsulation is ARPA
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
To display information about neighbors, use the show cdp neighbors privileged EXEC command.
show cdp neighbors [interface-type interface-number] [detail]
interface-type | (Optional) Type of the interface connected to the neighbors about which you want information. |
interface-number | (Optional) Number of the interface connected to the neighbors about which you want information. |
detail | (Optional) Displays detailed information about a neighbor (or neighbors) including network address, enabled protocols, hold time, and software version. |
Privileged EXEC
The following is sample output from the show cdp neighbors command. Device ID, interface type and number, hold-time settings, capabilities, platform, and port ID information about the communication server's neighbors is displayed.
cs# show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP
Device ID Local Intrfce Holdtme Capability Platform Port ID
device.cisco.com Eth 0 151 R T AGS Eth 0
device.cisco.com Ser 0 165 R T AGS Ser 3
The following is sample output from the show cdp neighbors detail command. Additional detail is shown about the communication server's neighbors, including network address, enabled protocols, and software version:
cs# show cdp neighbors detail
Device ID: device.cisco.com
Entry address(es):
IP address: 198.92.68.18
CLNS address: 490001.1111.1111.1111.00
DECnet address: 10.1
Platform: AGS, Capabilities: Router Trans-Bridge
Interface: Ethernet0, Port ID (outgoing port): Ethernet0
Holdtime : 143 sec
Version :
GS Software (GS3), Experimental Version 10.2(10302) [asmith 161]
Copyright (c) 1986-1994 by cisco Systems, Inc.
Compiled Mon 07-Nov-94 14:34
show cdp entry
To display traffic information from the CDP table, use the show cdp traffic privileged EXEC command.
show cdp trafficThis command has no arguments or keywords.
Privileged EXEC
The following is sample output from the show cdp traffic command.
cs# show cdp traffic
CDP counters :
Packets output: 94, Input: 75
Hdr syntax: 0, Chksum error: 0, Encaps failed: 0
No memory: 0, Invalid packet: 0, Fragmented: 0
In this example, traffic information is displayed, which includes the numbers of packets sent, the number of packets received, header syntax, checksum errors, failed encapsulations, memory problems, and invalid and fragmented packet. Header syntax indicates the number of packets CDP receives that have an invalid header format.
To display the system clock, use the show clock EXEC command:
show clock [detail]
detail | (Optional) Indicates the clock source (NTP) and the current summer-time setting, if any. |
EXEC
The system clock keeps an "authoritative" flag that indicates whether or not the time is authoritative (believed to be accurate). If system clock has been set by a timing source (NTP), the flag is set. If the time is not authoritative, it will be used only for display purposes. Until the clock is authoritative and the "authoritative" flag is set, the flag prevents the communication server from causing peers to synchronize to itself when the communication server time is invalid.
The symbol that precedes the show clock display indicates the following:
| Symbol | Description |
|---|---|
* | Time is not authoritative. |
(blank) | Time is authoritative. |
. | Time is authoritative, but NTP is not synchronized. |
The following sample output shows that the current clock is authoritative and that the time source is NTP:
cs# show clock detail
15:29:03.158 PST Mon Mar 1 1993
Time source is NTP
cs#
clock set
show calendar
To display information about the types of CDP debugging that are enabled for your communication server, use the show debugging privileged EXEC command.
show debuggingThis command has no arguments or keywords.
Privileged EXEC
The following is sample output from the show debug command:
cs# show debugging
CDP:
CDP packet info debugging is on
CDP events debugging is on
CDP neighbor info debugging is on
CDP-PA: Packet received from neon.cisco.com on interface Ethernet0
CDP-EV: Encapsulation on interface Serial0 failed
CDP-AD: Aging entry for neon.cisco.com, on interface Ethernet0
In this example, all three types of CDP debugging are enabled.
See the Debug Command Reference for more information about the CDP debugging commands.
debug cdp packets
debug cdp adjacency
debug cdp events
To display the active accounting or checkpointed database or to display access-list violations, use the show ip accounting privileged EXEC command.
show ip accounting [checkpoint] [output-packets | access-violations]
checkpoint | (Optional) Indicates that the checkpointed database should be displayed. |
output-packets | (Optional) Indicates that information pertaining to packets that passed access control and were successfully routed should be displayed. This is the default value if neither output-packets nor access-violations is specified. |
access-violations | (Optional) Indicates that information pertaining to packets that failed access lists and were not routed should be displayed. |
If neither the output-packets nor access-violations keyword is specified, show ip accounting displays information pertaining to packets that passed access control and were successfully routed.
EXEC
To use this command, you must first enable IP accounting on a per-interface basis.
The following example displays information pertaining to packets that failed access lists and were not router (see sample display for command).
show ip accounting access-violations
Following is sample output from the show ip accounting command:
cs# show ip accounting
Source Destination Packets Bytes
131.108.19.40 192.67.67.20 7 306
131.108.13.55 192.67.67.20 67 2749
131.108.2.50 192.12.33.51 17 1111
131.108.2.50 130.93.2.1 5 319
131.108.2.50 130.93.1.2 463 30991
131.108.19.40 130.93.2.1 4 262
131.108.19.40 130.93.1.2 28 2552
131.108.20.2 128.18.6.100 39 2184
131.108.13.55 130.93.1.2 35 3020
131.108.19.40 192.12.33.51 1986 95091
131.108.2.50 192.67.67.20 233 14908
131.108.13.28 192.67.67.53 390 24817
131.108.13.55 192.12.33.51 214669 9806659
131.108.13.111 128.18.6.23 27739 1126607
131.108.13.44 192.12.33.51 35412 1523980
192.31.7.21 130.93.1.2 11 824
131.108.13.28 192.12.33.2 21 1762
131.108.2.166 192.31.7.130 797 141054
131.108.3.11 192.67.67.53 4 246
192.31.7.21 192.12.33.51 15696 695635
192.31.7.24 192.67.67.20 21 916
131.108.13.111 128.18.10.1 16 1137
Table 5-19 describes significant fields shown in the display.
| Field | Description |
|---|---|
Source | Source address of the packet |
Destination | Destination address of the packet |
Packets | Number of packets transmitted from the source address to the destination address |
Bytes | Number of bytes transmitted from the source address to the destination address |
Following is sample output from the show ip accounting access-violations command:
cs# show ip accounting access-violations
Source Destination Packets Bytes ACL
131.108.19.40 192.67.67.20 7 306 77
131.108.13.55 192.67.67.20 67 2749 185
131.108.2.50 192.12.33.51 17 1111 140
131.108.2.50 130.93.2.1 5 319 140
131.108.19.40 130.93.2.1 4 262 77
Accounting data age is 41
Table 5-20 describes significant fields shown in the display.
| Field | Description |
|---|---|
Source | Source address of the packet |
Destination | Destination address of the packet |
Packets | For accounting keyword, number of packets transmitted from the source address to the destination address For access-violations keyword, number of packets transmitted from the source address to the destination address that violated the access control list |
Bytes | For accounting keyword, number of bytes transmitted from the source address to the destination address For access-violations keyword, number of bytes transmitted from the source address to the destination address that violated the access-control list |
ACL | Number of the access list of the last packet transmitted from the source to the destination that failed an access list |
clear ip accounting
ip accounting
ip accounting-list
ip accounting-threshold
ip accounting-transits
Use the show logging EXEC command to display the state of logging (syslog).
show loggingThis command has no arguments or keywords.
EXEC
This command displays the state of syslog error and event logging, including host addresses, and whether console logging is enabled. This command also displays Simple Network Management Protocol (SNMP) configuration parameters and protocol activity.
The following is sample output from the show logging command:
cs# show logging
Syslog logging: enabled
Console logging: disabled
Monitor logging: level debugging, 266 messages logged.
Trap logging: level informational, 266 messages logged.
Logging to 131.108.2.238
SNMP logging: disabled, retransmission after 30 seconds
0 messages logged
Table 5-21 describes significant fields shown in the display.
| Field | Description |
|---|---|
Syslog logging | When enabled, system logging messages are sent to a UNIX host that acts as a syslog server; that is, it captures and saves the messages. |
Console logging | If enabled, states the level; otherwise, this field displays disabled. |
Monitor logging | Minimum level of severity required for a log message to be sent to a monitor terminal (not the console). |
Trap logging | Minimum level of severity required for a log message to be sent to a syslog server. |
SNMP logging | Shows whether SNMP logging is enabled and the number of messages logged, and the retransmission interval. |
type | (Optional) Memory type to display (processor, multibus, io, sram). If type is not specified, statistics for all memory types present in the communication server will be displayed. |
free | (Optional) Displays free memory statistics. |
EXEC
The following is sample output from the show memory command:
cs# show memory
Head FreeList Total(b) Used(b) Free(b) Largest(b)
Processor 2E0FF8 2AABFC 13758472 847216 12911256 12908036
Processor memory
Address Bytes Prev. Next Ref PrevF NextF Alloc PC What
2E0FF8 2128 0 2E1848 1 84352 *Init*
2E1848 2052 2E0FF8 2E204C 1 86184 *Init*
2E204C 564 2E1848 2E2280 1 861B0 *Init*
2E2280 2052 2E204C 2E2A84 1 1266 *Init*
2E2A84 308 2E2280 2E2BB8 1 44974 *Init*
2E2BB8 220 2E2A84 2E2C94 1 3F788 *Init*
2E2C94 2052 2E2BB8 2E3498 1 3F7A8 *Init*
2E3498 4052 2E2C94 2E446C 1 46770 *Init*
2E446C 516 2E3498 2E4670 1 44E4C *Packet Buffer*
2E4670 516 2E446C 2E4874 1 44E4C *Packet Buffer*
2E4874 516 2E4670 2E4A78 1 44E4C *Packet Buffer*
2E4A78 516 2E4874 2E4C7C 1 44E4C *Packet Buffer*
2E4C7C 516 2E4A78 2E4E80 1 44E4C *Packet Buffer*
2E4E80 516 2E4C7C 2E5084 1 44E4C *Packet Buffer*
2E5084 516 2E4E80 2E5288 1 44E4C *Packet Buffer*
2E5288 516 2E5084 2E548C 1 44E4C *Packet Buffer*
2E548C 516 2E5288 2E5690 1 44E4C *Packet Buffer*
2E5690 516 2E548C 2E5894 1 44E4C *Packet Buffer*
The following is sample output from the show memory free command:
cs# show memory free
Head FreeList Total(b) Used(b) Free(b) Largest(b)
Processor 2E0FF8 2AABFC 13758472 847120 12911352 12908036
Processor memory
Address Bytes Prev. Next Ref PrevF NextF Alloc PC What
72 Free list 1
88 Free list 2
96 Free list 3
384A04 96 38496C 384A64 0 0 0 1205A4 IGRP Router
108 Free list 4
124 Free list 5
Final freespace block
3B09FC 12908036 3B0834 0 0 0 0 76162 (coalesced)
The display of show memory free contains the same types of information as the show memory display, except that only free memory is displayed, and the information is displayed in order for each free list.
The first section of the display includes summary statistics about the activities of the system memory allocator. Table 5-22 describes significant fields shown in the first section of the display.
| Field | Description |
|---|---|
Head | Hexadecimal address of the head of the memory allocation chain |
FreeList | Hexadecimal address of the base of the free list |
Total (b) | Sum of used bytes plus free bytes |
Used (b) | Amount of memory in use |
Free (b) | Amount of memory not in use |
Largest (b) | Size of largest available free block |
The second section of the display is a block-by-block listing of memory use. Table 5-23 describes significant fields shown in the second section of the display.
| Field | Description |
|---|---|
Address | Hexadecimal address of block |
Bytes | Size of block in bytes |
Prev. | Address of previous block (should match Address on previous line) |
Next | Address of next block (should match address on next line) |
Ref | Reference count for that memory block, indicating how many different processes are using that block of memory |
PrevF | Address of previous free block (if free) |
NextF | Address of next free block (if free) |
Alloc PC | Address of the system call that allocated the block |
What | Name of process that owns the block, or "(fragment)" if the block is a fragment, or "(coalesced)" if the block was coalesced from adjacent free blocks |
The show memory io command displays the free IO memory blocks. On the Cisco 2500, this command quickly shows how much unused IO memory is available.
The following is sample output from the show memory io command:
cs1# show memory io
I/O memory
Address Bytes Prev. Next Ref PrevF NextF Alloc PC What
100000 212 0 1000F8 1 3000F2C *Packet Data*
1000F8 212 100000 1001F0 1 3000F2C *Packet Data*
1001F0 212 1000F8 1002E8 1 3000F2C *Packet Data*
. . . . . . .
. . . . . . .
. . . . . . .
14AB94 4528 14A510 14BD68 0 146134 0 0 (fragment)
14BD68 1632 14AB94 14C3EC 1 3001C74 *Packet Data*
14C3EC 736240 14BD68 0 0 0 0 0 (fragment)
The show memory command on the Cisco 2500 includes information about processor and IO memory, and appears as follows:
cs1# show memory
Head FreeList Total(b) Used(b) Free(b) Largest(b)
Processor 66ABC 2DD1C 628036 579460 48576 36096
I/O 100000 32A14 1048576 179192 869384 736240
Processor memory
Address Bytes Prev. Next Ref PrevF NextF Alloc PC What
66ABC 2408 0 67448 1 30196A0 TTY data
67448 2000 66ABC 67C3C 1 301B640 TTY Input Buf
. . . . . . .
. . . . . . .
. . . . . . .
14AB94 4528 14A510 14BD68 0 146134 14542C 0 (fragment)
14BD68 1632 14AB94 14C3EC 1 3001C74 *Packet Data*
14C3EC 736240 14BD68 0 0 0 0 0 (fragment)
cs1#
To show the status of Network Time Protocol (NTP) associations, use the show ntp associations EXEC command.
show ntp associations [detail]
detail | (Optional) Shows detailed information about each NTP association. |
EXEC
Detailed descriptions of the information displayed by this command can be found in the NTP specification (RFC 1305).
The following is sample output from the show ntp associations command:
cs# show ntp associations
address ref clock st when poll reach delay offset disp
~160.89.32.2 160.89.32.1 5 29 1024 377 4.2 -8.59 1.6
+~131.108.13.33 131.108.1.111 3 69 128 377 4.1 3.48 2.3
*~131.108.13.57 131.108.1.111 3 32 128 377 7.9 11.18 3.6
* master (synced), # master (unsynced), + selected, - candidate, ~ configured
Table 5-24 describes significant fields shown in the display.
| Field | Description |
|---|---|
(leading characters in display lines) | The first characters in a display line can be one or more of the following characters: * Synchronized to this peer |
address | Address of peer. |
ref clock | Address of peer's reference clock. |
st | Peer's stratum. |
when | Time since last NTP packet received from peer. |
poll | Polling interval (seconds). |
reach | Peer reachability (bit string, in octal). |
delay | Round-trip delay to peer (milliseconds). |
offset | Relative time of peer's clock to local clock (milliseconds). |
disp | Dispersion |
The following is sample output of the show ntp associations detail command:
cs# show ntp associations detail
160.89.32.2 configured, insane, invalid, stratum 5
ref ID 160.89.32.1, time AFE252C1.6DBDDFF2 (00:12:01.428 PDT Mon Jul 5 1993)
our mode active, peer mode active, our poll intvl 1024, peer poll intvl 64
root delay 137.77 msec, root disp 142.75, reach 376, sync dist 215.363
delay 4.23 msec, offset -8.587 msec, dispersion 1.62
precision 2**19, version 3
org time AFE252E2.3AC0E887 (00:12:34.229 PDT Mon Jul 5 1993)
rcv time AFE252E2.3D7E464D (00:12:34.240 PDT Mon Jul 5 1993)
xmt time AFE25301.6F83E753 (00:13:05.435 PDT Mon Jul 5 1993)
filtdelay = 4.23 4.14 2.41 5.95 2.37 2.33 4.26 4.33
filtoffset = -8.59 -8.82 -9.91 -8.42 -10.51 -10.77 -10.13 -10.11
filterror = 0.50 1.48 2.46 3.43 4.41 5.39 6.36 7.34
131.108.13.33 configured, selected, sane, valid, stratum 3
ref ID 131.108.1.111, time AFE24F0E.14283000 (23:56:14.078 PDT Sun Jul 4 1993)
our mode client, peer mode server, our poll intvl 128, peer poll intvl 128
root delay 83.72 msec, root disp 217.77, reach 377, sync dist 264.633
delay 4.07 msec, offset 3.483 msec, dispersion 2.33
precision 2**6, version 3
org time AFE252B9.713E9000 (00:11:53.442 PDT Mon Jul 5 1993)
rcv time AFE252B9.7124E14A (00:11:53.441 PDT Mon Jul 5 1993)
xmt time AFE252B9.6F625195 (00:11:53.435 PDT Mon Jul 5 1993)
filtdelay = 6.47 4.07 3.94 3.86 7.31 7.20 9.52 8.71
filtoffset = 3.63 3.48 3.06 2.82 4.51 4.57 4.28 4.59
filterror = 0.00 1.95 3.91 4.88 5.84 6.82 7.80 8.77
131.108.13.57 configured, our_master, sane, valid, stratum 3
ref ID 131.108.1.111, time AFE252DC.1F2B3000 (00:12:28.121 PDT Mon Jul 5 1993)
our mode client, peer mode server, our poll intvl 128, peer poll intvl 128
root delay 125.50 msec, root disp 115.80, reach 377, sync dist 186.157
delay 7.86 msec, offset 11.176 msec, dispersion 3.62
precision 2**6, version 2
org time AFE252DE.77C29000 (00:12:30.467 PDT Mon Jul 5 1993)
rcv time AFE252DE.7B2AE40B (00:12:30.481 PDT Mon Jul 5 1993)
xmt time AFE252DE.6E6D12E4 (00:12:30.431 PDT Mon Jul 5 1993)
filtdelay = 49.21 7.86 8.18 8.80 4.30 4.24 7.58 6.42
filtoffset = 11.30 11.18 11.13 11.28 8.91 9.09 9.27 9.57
filterror = 0.00 1.95 3.91 4.88 5.78 6.76 7.74 8.71
Table 5-25 describes significant fields shown in the display.
| Field | Descriptions |
|---|---|
configured | Peer was statically configured. |
dynamic | Peer was dynamically discovered. |
our_master | Local machine is synchronized to this peer. |
selected | Peer is selected for possible synchronization. |
candidate | Peer is a candidate for selection. |
sane | Peer passes basic sanity checks. |
insane | Peer fails basic sanity checks. |
valid | Peer time is believed to be valid. |
invalid | Peer time is believed to be invalid. |
leap_add | Peer is signaling that a leap second will be added. |
leap-sub | Peer is signaling that a leap second will be subtracted. |
unsynced | Peer is not synchronized to any other machine. |
ref ID | Address of machine peer is synchronized to. |
time | Last timestamp peer received from its master. |
our mode | Our mode relative to peer (active / passive / client / server / bdcast / bdcast client). |
peer mode | Peer's mode relative to us. |
our poll ivl | Our poll interval to peer. |
peer poll ivl | Peer's poll interval to us. |
root delay | Delay along path to root (ultimate stratum 1 time source). |
root disp | Dispersion of path to root. |
reach | Peer reachability (bit string in octal). |
sync dist | Peer synchronization distance. |
delay | Round-trip delay to peer. |
offset | Offset of peer clock relative to our clock. |
dispersion | Dispersion of peer clock. |
precision | Precision of peer clock in Hz. |
version | NTP version number that peer is using. |
org time | Originate timestamp. |
rcv time | Receive timestamp. |
xmt time | Transmit timestamp. |
filtdelay | Round-trip delay in milliseconds of each sample. |
filtoffset | Clock offset in milliseconds of each sample. |
filterror | Approximate error of each sample. |
To show the status of Network Time Protocol (NTP), use the show ntp status EXEC command.
show ntp statusThis command has no arguments or keywords.
EXEC
The following is sample output from the show ntp status command:
cs# show ntp status
Clock is synchronized, stratum 4, reference is 131.108.13.57
nominal freq is 250.0000 Hz, actual freq is 249.9990 Hz, precision is 2**19
reference time is AFE2525E.70597B34 (00:10:22.438 PDT Mon Jul 5 1993)
clock offset is 7.33 msec, root delay is 133.36 msec
root dispersion is 126.28 msec, peer dispersion is 5.98 msec
Table 5-26 shows the significant fields in the display.
| Field | Description |
|---|---|
synchronized | System is synchronized to an NTP peer. |
unsynchronized | System is not synchronized to any NTP peer. |
stratum | NTP stratum of this system. |
reference | Address of peer we are synchronized to. |
nominal freq | Nominal frequency of system hardware clock. |
actual freq | Measured frequency of system hardware clock. |
precision | Precision of this system's clock (in Hz). |
reference time | Reference timestamp. |
clock offset | Offset of our clock to synchronized peer. |
root delay | Total delay along path to root clock. |
root dispersion | Dispersion of root path. |
peer dispersion | Dispersion of synchronized peer. |
To display your current level of privilege, use the show privilege EXEC command.
show privilegeThis command has no arguments or keywords.
EXEC
The following is sample output from the show privilege command. The current privilege level is 15.
cs# show privilege
Current privilege level is 15
enable password level
Use the show processes EXEC command to display information about the active processes.
show processes [cpu]
cpu | (Optional) Displays detailed CPU utilization statistics. |
EXEC
The following is sample output from the show processes command:
cs# show processes
CPU utilization for five seconds: 0%/0%; one minute: 0%; five minutes: 0%
PID Q T PC Runtime (ms) Invoked uSecs Stacks TTY Process
1 M T 40FD4 1736 58 29931 910/1000 0 Check heaps
2 H E 9B49C 68 585 116 790/900 0 IP Input
3 M E AD4E6 0 737 0 662/1000 0 TCP Timer
4 L E AEBB2 0 2 0 896/1000 0 TCP Protocols
5 M E A2F9A 0 1 0 852/1000 0 BOOTP Server
6 L E 4D2A0 16 127 125 876/1000 0 ARP Input
7 L E 50C76 0 1 0 936/1000 0 Probe Input
8 M E 63DA0 0 7 0 888/1000 0 MOP Protocols
9 M E 86802 0 2 0 1468/1500 0 Timers
10 M E 7EBCC 692 64 10812 794/1000 0 Net Background
11 L E 83BBC 0 5 0 870/1000 0 Logger
12 M T 11C454 0 38 0 574/1000 0 BGP Open
13 H E 7F0E0 0 1 0 446/500 0 Net Input
14 M T 436EA 540 3435 157 737/1000 0 TTY Background
15 M E 11BA9C 0 1 0 960/1000 0 BGP I/O
16 M E 11553A 5100 1367 3730 1250/1500 0 IGRP Router
17 M E 11B76C 88 4200 20 1394/1500 0 BGP Router
18 L T 11BA64 152 14650 10 942/1000 0 BGP Scanner
19 M * 0 192 80 2400 1714/2000 0 Exec
The following is sample output from the show processes cpu command:
cs# show processes cpu
CPU utilization for five seconds: 5%/2%; one minute: 3%; five minutes: 2%
PID Runtime (ms) Invoked uSecs 5Sec 1Min 5Min Process
1 1736 58 29931 0% 0% 0% Check heaps
2 68 585 116 1% 1% 0% IP Input
3 0 744 0 0% 0% 0% TCP Timer
4 0 2 0 0% 0% 0% TCP Protocols
5 0 1 0 0% 0% 0% BOOTP Server
6 16 130 123 0% 0% 0% ARP Input
7 0 1 0 0% 0% 0% Probe Input
8 0 7 0 0% 0% 0% MOP Protocols
9 0 2 0 0% 0% 0% Timers
10 692 64 10812 0% 0% 0% Net Background
11 0 5 0 0% 0% 0% Logger
12 0 38 0 0% 0% 0% BGP Open
13 0 1 0 0% 0% 0% Net Input
14 540 3466 155 0% 0% 0% TTY Background
15 0 1 0 0% 0% 0% BGP I/O
16 5100 1367 3730 0% 0% 0% IGRP Router
17 88 4232 20 2% 1% 0% BGP Router
18 152 14650 10 0% 0% 0% BGP Scanner
19 224 99 2262 0% 0% 1% Exec
Table 5-27 describes significant fields shown in the two displays. In the first line of the display: CPU utilization for the last 5 seconds, 1 minute, and 5 minutes. The second part of the 5-second figure is the percentage of the CPU used by interrupt routines.
| Field | Description |
|---|---|
five seconds | CPU utilization by task in last 5 seconds. |
one minute | CPU utilization by task in last minute. |
five minutes | CPU utilization by task in last 5 minutes. |
PID | Process ID. |
Q | Process queue priority. Possible values: H (high), M (medium), L (low). |
T | Scheduler test. Possible values: E (event), T (time), S (suspended). |
PC | Current program counter. |
Runtime (ms) | CPU time the process has used, in milliseconds. |
Invoked | Number of times the process has been invoked. |
uSecs | Microseconds of CPU time for each process invocation. |
Stacks | Low water mark/Total stack space available. |
TTY | Terminal that controls the process. |
Process | Name of process. |
Use the show processes memory EXEC command to show memory utilization.
show processes memoryThis command has no arguments or keywords.
EXEC
The following is sample output from the show processes memory command:
cs# show processes memory
Total: 2416588, Used: 530908, Free: 1885680
PID TTY Allocated Freed Holding Process
0 0 462708 2048 460660 *Init*
0 0 76 4328 - 4252 *Sched*
0 0 82732 33696 49036 *Dead*
1 0 2616 0 2616 Net Background
2 0 0 0 0 Logger
21 0 20156 40 20116 IGRP Router
4 0 104 0 104 BOOTP Server
5 0 0 0 0 IP Input
6 0 0 0 0 TCP Timer
7 0 360 0 360 TCP Protocols
8 0 0 0 0 ARP Input
9 0 0 0 0 Probe Input
10 0 0 0 0 MOP Protocols
11 0 0 0 0 Timers
12 0 0 0 0 Net Input
Table 5-28 describes significant fields shown in the display.
| Field | Description |
|---|---|
Total | Total amount of memory held. |
PID | Process ID. |
TTY | Terminal that controls the process. |
Allocated | Sum of all memory that process has requested from the system. |
Freed | How much memory a process has returned to the system. |
Holding | Allocated memory minus freed memory. A value can be negative when it has freed more than it was allocated. |
Process | Process name. |
*Init* | System initialization. |
*Sched* | The scheduler. |
*Dead* | Processes as a group that are now dead. |
This command has no arguments or keywords.
EXEC
The following is sample output from the show protocols command:
cs# show protocols
Global values:
Internet Protocol routing is enabled
X.25 routing is enabled
Ethernet 0 is up, line protocol is up
Internet address is 131.108.1.1, subnet mask is 255.255.255.0
Serial 0 is up, line protocol is up
Internet address is 192.31.7.49, subnet mask is 255.255.255.240
Ethernet 1 is up, line protocol is up
Internet address is 131.108.2.1, subnet mask is 255.255.255.0
Serial 1 is down, line protocol is down
Internet address is 192.31.7.177, subnet mask is 255.255.255.240
For more information on the parameters or protocols shown in this sample output, refer to the Access and Communication Servers Configuration Guide.
To list the current state of the queue lists, use the show queueing privileged EXEC command.
show queueing [custom | priority]
custom | (Optional) Shows status of custom queue lists. |
priority | (Optional) Shows status of priority lists. |
Privileged EXEC
If no keyword is entered, this command show the status of both custom and priority queue lists.
The following is sample output from the show queueing custom EXEC command:
cs# show queueing custom
Current custom queue configuration:
List Queue Args
3 10 default
3 3 interface Tunnel3
3 3 protocol ip
3 3 byte-count 444 limit 3
custom-queue-list
priority-group
priority-list interface
priority-list queue-limit
queue-list default
queue-list interface
queue-list protocol
queue-list queue byte-count
queue-list queue limit
To check the status of communications between the SNMP agent and SNMP manager, use the
show snmp EXEC command.
This command has no arguments or keywords.
EXEC
This command provides counter information for RFC 1213 SNMP operations. It also displays the chassis ID string defined with the snmp-server chassis-id command.
The following is sample output from the show snmp command:
cs# show snmp
Chassis: SN#TS02K229
167 SNMP packets input
0 Bad SNMP version errors
0 Unknown community name
0 Illegal operation for community name supplied
0 Encoding errors
167 Number of requested variables
0 Number of altered variables
0 Get-request PDUs
167 Get-next PDUs
0 Set-request PDUs
167 SNMP packets output
0 Too big errors (Maximum packet size 484)
0 No such name errors
0 Bad values errors
0 General errors
167 Get-response PDUs
0 SNMP trap PDUs
snmp-server chassis-id
Use the show stacks EXEC command to monitor the stack utilization of processes and interrupt routines.
show stacksThis command has no arguments or keywords.
EXEC
The display from this command includes the reason for the last system reboot. If the system was reloaded because of a system failure, a saved system stack trace is displayed. This information is of use only to your technical support representative in analyzing crashes in the field. It is included here in case you need to read the displayed statistics to an engineer over the phone.
The following is sample output from the show stacks command following a system failure:
cs# show stacks
Minimum process stacks:
Free/Size Name
652/1000 Router Init
726/1000 Init
744/1000 BGP Open
686/1200 Virtual Exec
Interrupt level stacks:
Level Called Free/Size Name
1 0 1000/1000 env-flash
3 738 900/1000 Multiport Communications Interfaces
5 178 970/1000 Console UART
System was restarted by bus error at PC 0xAD1F4, address 0xD0D0D1A
GS Software (GS3), Version 9.1(0.16), BETA TEST SOFTWARE
Compiled Tue 11-Aug-92 13:27 by jthomas
Stack trace from system failure:
FP: 0x29C158, RA: 0xACFD4
FP: 0x29C184, RA: 0xAD20C
FP: 0x29C1B0, RA: 0xACFD4
FP: 0x29C1DC, RA: 0xAD304
FP: 0x29C1F8, RA: 0xAF774
FP: 0x29C214, RA: 0xAF83E
FP: 0x29C228, RA: 0x3E0CA
FP: 0x29C244, RA: 0x3BD3C
Use the show tcp EXEC command to display the status of TCP connections.
show tcp [line-number]
line-number | (Optional) Absolute line number of the line for which you want to display Telnet connection status |
EXEC
The following is sample output from the show tcp command:
cs# show tcp
con0 (console terminal), connection 1 to host MATHOM
Connection state is ESTAB, I/O status: 1, unread input bytes: 1
Local host: 192.31.7.18, 33537 Foreign host: 192.31.7.17, 23
Enqueued packets for retransmit: 0, input: 0, saved: 0
Event Timers (current time is 2043535532):
Timer: Retrans TimeWait AckHold SendWnd KeepAlive
Starts: 69 0 69 0 0
Wakeups: 5 0 1 0 0
Next: 2043536089 0 0 0 0
iss: 2043207208 snduna: 2043211083 sndnxt: 2043211483 sndwnd: 1344
irs: 3447586816 rcvnxt: 3447586900 rcvwnd: 2144 delrcvwnd: 83
RTTO: 565 ms, RTV: 233 ms, KRTT: 0 ms, minRTT: 68 ms, maxRTT: 1900 ms
ACK hold: 282 ms
Datagrams (max data segment is 536 bytes):
Rcvd: 106 (out of order: 0), with data: 71, total data bytes: 83
Sent: 96 (retransmit: 5), with data: 92, total data bytes: 4678
Table 5-29 describes the following lines of output shown in the display:
con0 (console terminal), connection 1 to host MATHOM
Connection state is ESTAB, I/O status: 1, unread input bytes: 1
Local host: 192.31.7.18, 33537 Foreign host: 192.31.7.17, 23
Enqueued packets for retransmit: 0, input: 0, saved: 0
| Field | Description |
|---|---|
con0 | Identifying number of the line. |
(console terminal) | Location string. |
connection 1 | Number identifying the TCP connection. |
to host MATHOM | Name of the remote host to which the connection has been made. |
Connection state is ESTAB | A connection progresses through a series of states during its lifetime. These states follow in the order in which a connection progresses through them.
For more information, see RFC 793, Transmission Control Protocol Functional Specification. |
I/O status: 1 | Number describing the current internal status of the connection. |
unread input bytes: 1 | Number of bytes that the lower-level TCP processes have read, but the higher level TCP processes have not yet processed. |
Local host: 192.31.7.18 | IP address of the network server. |
33537 | Local port number, as derived from the following equation: line-number + (512 * random-number). (The line number uses the lower nine bits; the other bits are random.) |
Foreign host: 192.31.7.17 | IP address of the remote host to which the TCP connection has been made. |
23 | Destination port for the remote host. |
Enqueued packets for retransmit: 0 | Number of packets waiting on the retransmit queue. These are packets on this TCP connection that have been sent but have not yet been acknowledged by the remote TCP host. |
input: 0 | Number of packets that are waiting on the input queue to be read by the user. |
saved: 0 | Number of received out-of-order packets that are waiting for all packets comprising the message to be received before they enter the input queue. For example, if packets 1, 2, 4, 5, and 6 have been received, packets 1 and 2 would enter the input queue, and packets 4, 5, and 6 would enter the saved queue. |
The following line of output shows the current time according to the system clock of the local host:
Event Timers (current time is 2043535532):
The time shown is the number of milliseconds since the system started.
The following lines of output display the number of times that various local TCP timeout values were reached during this connection. In this example, the communication server retransmitted 69 times because it received no response from the remote host, and it transmitted an acknowledgment many more times because there was no data on which to piggyback.
Timer: Retrans TimeWait AckHold SendWnd KeepAlive
Starts: 69 0 69 0 0
Wakeups: 5 0 1 0 0
Next: 2043536089 0 0 0 0
Table 5-30 describes the fields in the preceding lines of output.
| Field | Description |
|---|---|
Timer: | The names of the timers in the display. |
Starts: | The number of times the timer has been started during this connection. |
Wakeups: | Number of keepalives transmitted without receiving any response. (This field is reset to zero when a response is received.) |
Next: | The system clock setting that will trigger the next time this timer will go off. |
Retrans | The Retransmission timer is used to time TCP packets that have not been acknowledged and are waiting for retransmission. |
TimeWait | The TimeWait timer is used to ensure that the remote system receive a request to disconnect a session. |
AckHold | The Acknowledgment timer is used to delay the sending of acknowledgments to the remote TCP in an attempt to reduce network use. |
SendWnd | The Send Window is used to ensure that there is no closed window due to a lost TCP acknowledgment. |
KeepAlive | The KeepAlive timer is used to control the transmission of test messages to the remote TCP to ensure that the link has not been broken without the local TCP's knowledge. |
The following lines of output display the sequence numbers that TCP uses to ensure sequenced, reliable transport of data. The communication server and remote host each use these sequence numbers for flow control and to acknowledge receipt of datagrams. Table 5-31 describes the specific fields in these lines of output:
iss: 2043207208 snduna: 2043211083 sndnxt: 2043211483 sndwnd: 1344
irs: 3447586816 rcvnxt: 3447586900 rcvwnd: 2144 delrcvwnd: 83
| Field | Description |
|---|---|
| Initial send sequence number. |
| Last send sequence number the communication server has sent but has not received an acknowledgment for. |
| Sequence number the communication server will send next. |
| TCP window size of the remote host. |
| Initial receive sequence number. |
| Last receive sequence number the communication server has acknowledged. |
| Communication server's TCP window size. |
| Delayed receive window—data the communication server has read from the connection, but has not yet subtracted from the receive window the communication server has advertised to the remote host. The value in this field gradually increases until it is larger than a full-sized packet, at which point it is applied to the rcvwnd field. |
The following lines of output display values that the communication server uses to keep track of transmission times so that TCP can adjust to the network it is using. Table 5-32 describes the fields in the following line of output:
RTTO: 565 ms, RTV: 233 ms, KRTT: 0 ms, minRTT: 68 ms, maxRTT: 1900 ms
ACK hold: 282 ms
| Field | Description |
|---|---|
| Round-trip timeout. |
| Variance of the round-trip time. |
| New round-trip timeout (using the Karn algorithm). This field separately tracks the round-trip time of packets that have been retransmitted. |
| Smallest recorded round-trip timeout (hard wire value used for calculation). |
| Largest recorded round-trip timeout. |
| Time the communication server will delay an acknowledgment in order to piggyback data on it. |
For more information on these fields, refer to "Round Trip Time Estimation," P. Karn & C. Partridge, ACM SIGCOMM-87, August 1987.
Table 5-33 describes the fields in the following lines of output:
Datagrams (max data segment is 536 bytes):
Rcvd: 106 (out of order: 0), with data: 71, total data bytes: 83
Sent: 96 (retransmit: 5), with data: 92, total data bytes: 4678
| Field | Description |
|---|---|
Rcvd: 106 (out of order: 0) | Number of datagrams the local host has received during this connection (and the number of these datagrams that were out of order). |
with data: 71 | Number of these datagrams that contained data. |
total data bytes: 83 | Total number of bytes of data in these datagrams. |
Sent: 96 (retransmit: 5) | Number of datagrams the local host sent during this connection (and the number of these datagrams that had to be retransmitted). |
with data: 92 | Number of these datagrams that contained data. |
total data bytes: 4678 | Total number of bytes of data in these datagrams. |
To create or update an access policy, use the snmp-server access-policy global configuration command. Use the no form of this command to remove the specified access policy.
snmp-server access-policy destination-party source-party context
destination-party | Name of a previously defined party identified as the destination party or target for this access policy. This name serves as a label used to reference a record defined for this party through the snmp-server party command. A destination party performs management operations that are requested by a source party. |
source-party | Name of a previously defined party identified as the source party or subject for this access policy. This name serves as a label used to reference a record defined for this party through the snmp-server party command. A source party sends communications to a destination party requesting the destination party to perform management operations. |
context | Name of a previously defined context that defines the resources for the access policy. This name serves as a label used to reference a record defined for this context through the snmp-server context command. A context identifies object resources accessible to a party. |
privileges | Bit mask representing the access privileges that govern the management operations that the source party can ask the destination party to perform. Use decimal or hexadecimal format to specify privileges as a sum of values in which each value specifies an SNMP PDU type that the source party can use to request an operation. The decimal values are defined as follows:
|
volatile | (Optional) Indicates that the access policy will not be written to nonvolatile memory when the write memory command is given or to the terminal when the write terminal command is given. |
Global configuration
An access policy defines the management operations the destination party can perform in relation to resources defined by the specified context when requested by the source party. Access policies are defined on the router for communications from the manager to the agent; in this case, the agent is the destination party and the manager is the source party. Access policies can also be defined on the router for Response message and trap message communication from the agent to the manager; in this case, the manager is the destination party and the agent is the source party.
The first snmp-server command that you enter enables both versions of SNMP.
The following example configures an access policy providing the manager with read-only access to the agent:
snmp-server access-policy agt1 mgr1 ctx1 0x23
The following example configures an access policy providing the manager with read-write access to the agent:
snmp-server access-policy agt2 mgr2 ctx2 43
The following example configures an access policy that allows responses and SNMP v.2 traps to be sent from the agent to a management station:
snmp-server access-policy mgr1 agt1 ctx1 132
The following example removes the access policy configured for the destination party named agt1, the source party named mgr1, and with a context named ctx1.
no snmp-server access-policy agt1 mgr1 ctx1
snmp-server party
snmp-server context
To provide a message line identifying the SNMP server serial number, use the snmp-server chassis-id global configuration command. Use the no form of this command to restore the default value, if any.
snmp-server chassis-id text
text | Message you want to enter to identify the chassis serial number |
On hardware platforms where the serial number can be machine-read, the default is the serial number.
Global configuration
The Cisco MIB provides a chassis MIB variable that enables the SNMP manager to gather data on system card descriptions, chassis type, chassis hardware version, chassis ID string, software version of ROM monitor, software version of system image in ROM, bytes of processor RAM installed, bytes of nonvolatile memory installed, bytes of nonvolatile memory in use, current configuration register setting, and the value of the configuration register at the next reload. The following installed card information is provided: type of card, serial number, hardware version, software version, and chassis slot number.
Use the show snmp command to see the chassis ID message.
In the following example, the chassis serial number specified is 1234456:
snmp-server chassis-id 1234456
show snmp
To set up the community access string to permit access to the SNMPv1 protocol, use the snmp-server community global configuration command. To remove the specified community string, use the no form of this command.
snmp-server community string [RO | RW] [number]
string | Community string that acts like a password and permits access to the SNMP protocol. |
RO | (Optional) Specifies read-only access. Authorized management stations are only able to retrieve MIB objects. |
RW | (Optional) Specifies read-write access. Authorized management stations are able to both retrieve and modify MIB objects. |
number | (Optional) Integer from 1 to 99 that specifies an access list of IP addresses that may use the community string to gain access to the SNMP v.1 agent. |
By default, an SNMP community string permits read-only access.
Global configuration
For the previous version of this command, the string argument was optional. The string argument is now required. However, to prevent errors and provide backward-compatibility, if the string option is omitted, a default value of public is assumed.
The no snmp-server command disables both versions of SNMP (SNMP v.1 and SNMP v.2).
The first snmp-server command that you enter enables both versions of SNMP.
The following example assigns the string comaccess to SNMP v.1 allowing read-only access and specifies that IP access list 4 can use the community string:
snmp-server community comaccess RO 4
The following example disables both versions of SNMP:
no snmp-server
snmp-server party
To set the system contact (syscontact) string, use the snmp-server contact global configuration command. Use the no form of this command to remove the system contact information.
snmp-server contact text
text | String that describes the system contact information |
No syscontact string is set.
Global configuration
The following is an example of a syscontact string:
snmp-server contact Dial System Operator at beeper # 27345
To create or update a context record, use the snmp-server context global configuration command. To remove the specified context entry, use the no form of this command.
snmp-server context context-name context-oid viewname [volatile]
context-name | Name of the context to be created or updated. This name serves as a label used to reference a record for this context. |
context-oid | Object identifier to assign to the context. Specify this value in dotted decimal notation, with an optional text identifier; for example, 1.3.6.1.6.3.3.1.4.131.108.45.11.1(== initialContextId.131.108.45.11.1). |
viewname | Name of a previously defined view. The view defines the objects available to the context. |
volatile | (Optional) Indicates that the entry identified by context-name will not be written to nonvolatile memory when the write memory command is given, or to the terminal when the write terminal command is given. |
General configuration
A context record identifies object resources accessible to a party. A context record is one of the components that make up an access policy. Therefore, you must configure a context record before you can create an access policy that includes the context. Context records and party records further codify MIB views.
To remove a context entry, specify only the name of the context. The name identifies the context to be deleted.
The first snmp-server command that you enter enables both versions of SNMP.
The following example shows how to create a context that includes all objects in the MIB-II subtree using a previously defined view named mib2:
snmp-server context mycontext initialContextid.131.108.24.56.3 mib2
A dagger (†) indicates that the command is documented in another chapter.
snmp-server view
write memory†
write terminal†
To specify the recipient of an SNMP trap operation, use the snmp-server host global configuration command. The no snmp-server host command removes the specified host.
snmp-server host host community-string [envmon] [framerelay] [sdlc] [snmp] [tty] [x25]
host | Name or Internet address of the host. |
community-string | Password-like community string to send with the trap operation. |
envmon | (Optional) Enables Cisco enterprise-specific environmental monitor traps to be sent to the trap receiver host when an environmental threshold has been exceeded. |
framerelay | (Optional) Enables Frame Relay traps to be sent to the trap receiver host. |
sdlc | (Optional) Enables SDLC traps to be sent to the trap receiver host. |
snmp | (Optional) Enables the SNMP traps defined in RFC 1157. |
tty | (Optional) Enables Cisco enterprise-specific traps when a TCP connection closes. |
x25 | (Optional) Enables X.25 event traps to be sent to host. |
No traps are sent.
If you enter the command with no keywords, the default is to enable all trap types.
Global configuration
The snmp-server host command specifies which host or hosts should receive SNMP traps. You need to issue the snmp-server host command once for each host acting as a trap recipient. When multiple snmp-server host commands are given, the community string in the last command is used, and in general, the trap types set in the last command will be used for all SNMP trap operations.
The following example sends the SNMP traps defined in RFC 1157 to the host specified by the name cisco.com. The community string is defined as the string comaccess.
snmp-server host cisco.com comaccess snmp
The following example sends the SNMP and Cisco enterprise-specific traps to address 131.108.2.160:
snmp-server host 131.108.2.160
snmp-server trap-timeout
To set the system location string, use the snmp-server location global configuration command. Use the no form of this command to remove the location string.
snmp-server location text
text | String that describes the system location information |
No system location string is set.
Global configuration
The following example illustrates a system location string:
snmp-server location Building 3/Room 214
To establish control over the largest SNMP packet size permitted when the SNMP server is receiving a request or generating a reply, use the snmp-server packetsize global configuration command. Use the no form of this command to restore the default value.
snmp-server packetsize byte-count
byte-count | Integer byte count from 484 to 8192 |
484 bytes
Global configuration
The following example establishes a packet filtering of a maximum size of 1024 bytes:
snmp-server packetsize 1024
To create or update a party record, use the snmp-server party global configuration command. To remove a specific party entry, use the no form of the command.
snmp-server party partyname party-oid [protocol-address] [packetsize size]
party-name | Name of the party characterized by the contents of the record. This name serves as a label used to reference the party record that you are creating or modifying. |
party-oid | Object identifier to assign to the party. Specify this value in dotted decimal notation, with an optional text identifier; for example, 1.3.6.1.6.3.3.1.3.131.108.34.54.1 (= initialPartyId.131.108.34.54.1) |
protocol-address | (Optional) Address of the protocol that the party record pertains to. Currently the only supported protocol is UDP, so this value specifies a UDP address in the format a.b.c.d port. In future releases, additional protocols will be supported.
This value is used to specify the destination of trap messages. |
packetsize size | Optional) Maximum size in bytes of a message that this party is able to receive. By default, the packet size set through the snmp-server packetsize command is used. |
local | remote | (Optional) Indicates that the party is local or remote. If neither local nor remote is specified, a default value of local is assumed. |
authentication | (Optional) Indicates that the party uses an authentication protocol. If specified, either md5 or snmpv1 is required. |
md5 key | Indicates that the party uses the Message Digest algorithm MD5 for message authentication. If md5 is specified, you must also specify a 16-byte hexadecimal ASCII string representing the MD5 authentication key for the party.
If specified with the keyword md5, all messages sent to this party will be authenticated using the SNMP v.2 MD5 authentication method with the key specified by key. |
clock clock | (Optional) Initial value of the authentication clock. |
lifetime lifetime | Lifetime, in seconds, that represents the upper bound on acceptable delivery delay for messages generated by the party. |
snmpv1 string | Community string. The keyword snmpv1 indicates that the party uses community-based authentication. All messages sent to this party will be authenticated using the SNMP v.1 community string specified by string instead of MD5. |
volatile | (Optional) Indicates that the entry identified by party-name will not be written to nonvolatile memory when the write memory command is given, or to the terminal when the write terminal command is given. |
If neither local nor remote is specified to indicate the location of the party, the party is assumed to be local.
If you do not specify a packet size value the packet size set through the snmp-server packetsize command is used.
General configuration
You define parties to identify managers and agents. An SNMP v.2 party identity is unique; it includes the logical network location of the party, characterized by the transport protocol domain and transport addressing information, and, optionally, an authentication method and its arguments.The authentication protocol reliably identifies the origin of all messages sent by the party. The authentication protocol also ensures the integrity of the messages; in other words, it ensures that the message received is the message that was sent.
Specifying md5 as the authentication method implies that this party record pertains to an SNMP v.2 party.
Specifying snmpv1 as the authentication method implies that this party record pertains to an SNMP v.1 party. This allows a management station that supports only SNMP v.1 to use SNMP v.2 MIB views. Instead of using the snmp-server community command, you can use the snmp-server party command with the snmpv1 keyword to define an SNMP v.1 party to be used to communicate with an SNMP v.1 management station. The snmp-server community command does not allow you to create MIB views for an SNMP v.1 management station.
If authentication is not specified, the party record pertains to an SNMP v.2 party, and no authentication will be performed for messages sent to this party.
To remove a party record, specify only the name of the party. The name identifies the party to be deleted.
The first snmp-server command that you enter enables both versions of SNMP.
The following example configures a remote unauthenticated party:
snmp-server party mgr1 initialPartyId.131.108.45.32.3 udp 131.108.45.76 162
The following example configures a local MD5-authenticated party with a large maximum packet size (You enter this command as a single line.):
snmp-server party agt1 initialPartyId.131.108.45.32.4 packetsize 1500 local
authentication md5 23de457623900ac3ef568fcb236589 lifetime 400
The following example configures an SNMP v.1 proxy party for the community public:
snmp-server party proxyv1 initialPartyId.131.108.45.32.100 authentication snmpv1 public
The following example removes the party named mgr1.
no snmp-server party mgr1
A dagger (†) indicates that the command is documented in another chapter.
snmp-server community
write memory†
write terminal†
To establish the message queue length for each trap host, use the snmp-server queue-length global configuration command.
snmp-server queue-length length
length | Integer that specifies the number of trap events that can be held before the queue must be emptied |
10 events
Global configuration
This command defines the length of the message queue for each trap host. Once a trap message is successfully transmitted, software will continue to empty the queue, but never faster than at a rate of four trap messages per second.
The following example establishes a message queue that traps four events before it must be emptied:
snmp-server queue-length 4
To use the SNMP message reload feature, the device configuration must include the snmp-server system-shutdown global configuration command. Use the no form of this command to prevent an SNMP system-shutdown request (from an SNMP manager) from resetting the Cisco agent.
snmp-server system-shutdownThis command has no arguments or keywords.
This command is not included in the configuration file.
Global configuration
The following example illustrates how to include the SNMP message reload feature in the device configuration:
snmp-server system-shutdown
To establish trap message authentication, use the snmp-server trap-authentication global configuration command. To remove message authentication, use the no form of this command.
snmp-server trap-authentication [snmp1 | snmp2]
snmpv1 | (Optional) Indicates that SNMP authentication traps will be sent to SNMP v.1 management stations only. |
snmpv2 | (Optional) Indicates that SNMP authentication traps will be sent to SNMP v.2 management stations only. |
Specifying the snmp-server trap-authentication command without a keyword turns on trap message authentication. In this case, messages are sent to the host that is specified though the snmp-server host command and to any SNMP stations configured through access policies to receive trap messages.
Global configuration
Specify the snmpv1 or snmpv2 keyword to indicate the type of management stations to send the trap messages to.
This command enables the router as an agent to send a trap message when it receives an SNMP v.1 packet with an incorrect community string or an SNMP v.2 packet with an incorrect MD5 authentication key.
The SNMP specification requires that a trap message be generated for each packet with an incorrect community string or authentication key; however, because this action can result in a security breach, the router (as an agent) by default does not send a trap message when it receives an incorrect community string or authentication key.
The community string or key is checked before any access list that may be set, so it is possible to get spurious trap messages. In other words, if you have issued an snmp-server community command with a specified access list, you may receive messages that come from someone that is not on the access list; in this case, an authentication trap is issued.The only workarounds are to disable trap authentication or to configure an access list on a router between the SNMP agent and the SNMP manager to prevent packets from getting to the SNMP agent.
To turn off all message authentication traps, use the no snmp-server trap-authentication without a keyword. To turn off message authentication traps only for SNMP v.1 stations or only for SNMP v.2 stations, give the negative form of the command with the appropriate keyword.
The first snmp-server command that you enter enables both versions of SNMP.
The following example illustrates how to enter the command that establishes trap message authentication:
snmp-server trap-authentication
snmp-server host
To specify the interface (and hence the corresponding IP address) that an SNMP trap should originate from, use the snmp-server trap-source global configuration command. Use the no form of this command to remove the source designation.
snmp-server trap-source interface
interface | Interface from which the SNMP trap originates. The argument includes the interface type and number in platform-specific syntax. |
No interface is specified.
Global configuration
When an SNMP trap is sent from a Cisco SNMP server, it has a trap address of whatever interface it happened to go out of at that time. Use this command if you want to use the trap address to trace particular needs.
The following example specifies that the IP address for Ethernet interface 0 is the source for all traps on the communication server:
snmp-server trap-source ethernet 0
To define how often to try resending trap messages on the retransmission queue, use the snmp-server trap-timeout global configuration command.
snmp-server trap-timeout seconds
seconds | Integer that sets the interval, in seconds, for resending the messages |
30 seconds
Global configuration
Before the communication server tries to send a trap, it looks for a route to the destination address. If there is no known route, the trap is saved in a retransmission queue. The server trap-timeout command determines the number of seconds between retransmission attempts.
The following example sets an interval of 20 seconds to try resending trap messages on the retransmission queue:
snmp-server trap-timeout 20
snmp-server host
To create or update an SNMP v.2 security context using the simplified security conventions method, use the snmp-server userid global configuration command. To remove a specified security context, use the no form of the command.
snmp-server userid user-id [view view-name] [RO | RW] [password password]
user-id | User ID name that identifies an approved SNMP v.2 user. The user ID represents a set of security information for this user. This value can identify a particular user of the system or a background process. |
view-name | (Optional) View to be used for this security context. The argument view-name must be the name of a predefined view. For authenticated users, defaults to the predefined view everything. For users who are not authenticated, defaults to the predefined view restricted. |
RO | (Optional) Specifies read-only access.This is the default for unauthenticated users. |
RW | (Optional) Specifies read-write access. This is the default for authenticated users. |
password password | (Optional) If specified, indicates that this is an authenticated user, and defines the password used to authenticate the user. The password must be at least eight characters long. |
For the snmp-server userid command, the default value for the view-name argument depends on whether the security context is password protected. Depending on whether the security context is password protected, one of the following default values applies:
These predefined views are described in RFC 1447.
Read-only access is the default for unauthenticated users.
Read-write access is the default for authenticated users.
Global configuration
The snmp-server userid command implements the simplified security conventions method of configuring the relationship between an agent and a manager. It provides a single-step method that offers an alternative to the access policy configuration method of defining this relationship. The simplified method offers ease-of-use at the cost of forfeiting control over certain values that can be configured if you create an access policy. The simplified security conventions method applies to a configuration in which the agent is the destination or recipient of messages and the manager is the source or sender of messages. You cannot use this command to define a relationship in which the agent is the source and the manager is the destination. The security context created does not apply to trap messages.
| Caution Use the simplified security conventions configuration method only if the management station participating in the manager-agent relationship also supports this method. |
If you provide a password, the password is encrypted on write operations for which encryption is enabled.
If you use the snmp-server userid command, the SNMP v.2 implementation assumes default values that it determines internally for required information that you cannot provide through the command interface. SNMP v.2 uses the following methods to determine these values:
The first snmp-server command that you enter enables both versions of SNMP.
The following example configures a security context for the user harold, who is unauthenticated, uses the view default, and has read-only access:
snmp-server userid harold
snmp-server access-policy
snmp-server context
snmp-server party
snmp-server view
To create or update a view entry, use the snmp-server view global configuration command. To remove the specified SNMP server view entry, use the no form of this command.
snmp-server view view-name oid-tree {included | excluded} [volatile]
view-name | Label for the view record that you are updating or creating. The name is used to reference the record. |
oid-tree | Object identifier of the ASN.1 subtree to be included or excluded from the view. To identify the subtree, specify a text string consisting of numbers, such as 1.3.6.2.4, or a word, such as system. Replace a single subidentifier with the asterisk (*) wildcard to specify a subtree family; for example 1.3.*.4. |
included | excluded | Type of view. Either included or excluded is required. |
volatile | (Optional) Indicates that the entry identified by view-name will not be written to nonvolatile memory when the write memory command is given or to the terminal when the write terminal command is given. |
Global configuration
Two standard predefined views can be used when a view is required, instead of defining a view. One is everything, which indicates that the user can see all objects. The other is default, which indicates that the user can see three groups: system, snmpStats, and snmpParties. The predefined views are described in RFC 1447.
Other SNMP v.2 commands require a predefined view as an argument. You use this command to define the view.
The first snmp-server command that you enter enables both versions of SNMP.
The following example creates a view that includes all objects in the MIB-II subtree:
snmp-server view mib2 mib-2 included
The following example creates a view that includes all objects in the MIB-II system group and all objects in the Cisco enterprise MIB:
snmp-server phred system included
snmp-server view phred cisco included
The following example creates a view that includes all objects in the MIB-II system group except for sysServices (System 7) and all objects for interface 1 in the MIB-II interfaces group:
snmp-server view agon system included
snmp-server view agon system.7 excluded
snmp-server view agon ifEntry.*.1 included
A dagger (†) indicates that the command is documented in another chapter.
snmp-server userid
snmp-server context
write memory†
write terminal†
To control the number of login attempts that can be made on a line set up for TACACS verification, use the tacacs-server attempts global configuration command. Use the no form of this command to remove this feature and restore the default.
tacacs-server attempts count
count | Integer that sets the number of attempts |
Three attempts
Global configuration
The following example changes the login attempt to just one try:
tacacs-server attempts 1
connection | Configures a required response when a user makes a TCP connection. |
enable | Configures a required response when a user enters the enable command. |
slip | Configures a required response when a user starts a SLIP or PPP session. |
always | (Optional) Performs authentication even when a user is not logged in. This option can be used with the connection or slip keywords. |
access-lists | (Optional) Requests and installs SLIP and PPP access lists. This option only applies to SLIP or PPP sessions, and can be used only with the slip keyword. |
Global configuration
If you use the enable use-tacacs command, you must also use tacacs-server authenticate enable; otherwise, you will be locked out of the communication server.
The following example illustrates how to configure TACACS logins that authenticate user TCP connections:
tacacs-server authenticate connection always
enable use-tacacs
To enable an extended TACACS mode, use the tacacs-server extended global configuration command. Use the no form of this command to disable the mode.
tacacs-server extendedThis command has no arguments or keywords.
Disabled
Global configuration
The following is an example of how to enable extended TACACS mode:
tacacs-server extended
To specify a TACACS host, use the tacacs-server host global configuration command. Use the no form of this command to delete the specified name or address.
tacacs-server host name
name | Name or IP address of the host |
No TACACS host is specified.
Global configuration
You can use multiple tacacs-server host commands to specify multiple hosts. The software searches for the hosts in the order you specify them.
The following example illustrates how to specify a TACACS host named SCACAT:
tacacs-server host SCACAT
A dagger (†) indicates that the command is documented in another chapter.
login tacacs †
ppp †
slip †
Use the tacacs-server key command to set the authentication/encryption key used for all TACACS+ communications between the access server and the TACACS+ daemon. To disable the key, use the no form of the command.
tacacs-server key key
key | The key used to set authentication and encryption. This key must match the key used on the TACACS+ daemon. |
Global Configuration
After enabling AAA with the aaa new-model command, you must set the authentication and encryption key using the tacas-server key command.
The key entered must match the key used on the TACACS+ daemon. All leading spaces are ignored, spaces within and at the end of the key are not. If you use spaces in your key, do not enclose the key in double quotes unless the quotes themselves are part of the key.
The following example illustrates how to set the authentication and encryption key to 'dare to go':
tacacs-server key dare to go
aaa new-model
To cause the network server to request the privileged password as verification, or to force successful login without further input from the user, use the tacacs-server last-resort global configuration command. Use the no form of this command to restore the system to the default behavior.
tacacs-server last-resort {password | succeed}
password | Allows the user to access the EXEC command mode by entering the password set by the enable command. |
succeed | Allows the user to access the EXEC command mode without further question. |
If, when running the TACACS server, the TACACS server does not respond, the default action is to deny the request.
Global configuration
Use the tacacs-server last-resort command to be sure that login can occur; for example, when a systems administrator needs to log in to troubleshoot TACACS servers that might be down.
The following example illustrates how to force successful login:
tacacs-server last-resort succeed
A dagger (†) indicates that the command is documented in another chapter.
enable password
login (exec) †
connection | Specifies that a message be transmitted when a user makes a TCP connection. |
enable | Specifies that a message be transmitted when a user enters the enable command. |
logout | Specifies that a message be transmitted when a user logs out. |
slip | Specifies that a message be transmitted when a user starts a SLIP or PPP session. |
always | (Optional) Sends a message even when a user is not logged in. This option only applies to SLIP or PPP sessions, and can be used with the connection, logout, or slip keywords. |
No message is transmitted to the TACACS server.
Global configuration
The terminal user receives an immediate response allowing access to the feature specified. Enter one of the keywords to specify notification of the TACACS server upon the corresponding action (when user logs out, for example).
The following example sets up notification of the TACACS server when a user logs out:
tacacs-server notify logout
To specify that the first TACACS request to a TACACS server be made without password verification, use the tacacs-server optional-passwords global configuration command. Use the no form of this command to restore the default.
tacacs-server optional-passwordsThis command has no arguments or keywords.
Disabled
Global configuration
When the user types in the login name, the login request is transmitted with the name and a zero-length password. If accepted, the login procedure completes. If the TACACS server refuses this request, the server software prompts for a password and tries again when the user supplies a password. The TACACS server must support authentication for users without passwords to make use of this feature. This feature supports all TACACS requests—login, SLIP, enable, and so on.
The following example illustrates how to configure the first login to not require TACACS verification:
tacacs-server optional-passwords
To specify the number of times the communication server software will search the list of TACACS server hosts before giving up, use the tacacs-server retransmit global configuration command. Use the no form of this command to restore the default.
tacacs-server retransmit retries
retries | Integer that specifies the retransmit count |
Two retries
Global configuration
The communication server software will try all servers, allowing each one to timeout before increasing the retransmit count.
The following example specifies a retransmit counter value of five times:
tacacs-server retransmit 5
To set the interval that the server waits for a server host to reply, use the tacacs-server timeout global configuration command. Use the no form of this command to restore the default.
tacacs-server timeout seconds
seconds | Integer that specifies the timeout interval in seconds |
5 seconds
Global configuration
The following example changes the interval timer to 10 seconds:
tacacs-server timeout 10
Use the trace user EXEC command to discover the IP routes the communication server's packets will actually take when traveling to their destination.
trace [protocol] [destination]
protocol | (Optional) The only protocol currently supported is ip. |
destination | (Optional) Destination address or host name on the command line. The default parameters for the appropriate protocol are assumed and the tracing action begins. |
The protocol argument is based on the communication server's examination of the format of the destination argument. For example, if the communication server finds a destination in IP format, the protocol defaults to ip.
user EXEC
The trace command works by taking advantage of the error messages generated by communication servers when a datagram exceeds its time-to-live (TTL) value.
The trace command starts by sending probe datagrams with a TTL value of one. This causes the first communication server to discard the probe datagram and send back an error message. The trace command sends several probes at each TTL level and displays the round-trip time for each.
The trace command sends out one probe at a time. Each outgoing packet may result in one or two error messages. A time exceeded error message indicates that an intermediate communication server has seen and discarded the probe. A destination unreachable error message indicates that the destination node has received the probe and discarded it because it could not deliver the packet. If the timer goes off before a response comes in, trace prints an asterisk (*).
Due to bugs in the IP implementation of various hosts and communication servers, the IP trace command might behave in odd ways.
Not all destinations will respond correctly to a probe message by sending back an ICMP port unreachable message. A long sequence of TTL levels with only asterisks, terminating only when the maximum TTL has been reached, might indicate this problem.
There is a known problem with the way some hosts handle an ICMP TTL exceeded message. Some hosts generate an ICMP message but they reuse the TTL of the incoming packet. Because this is zero, the ICMP packets do not make it back. When you trace the path to such a host, you might see a set of TTL values with asterisks (*). Eventually the TTL gets high enough that the ICMP message can get back. For example, if the host is six hops away, trace will time out on responses 6 through 11.
The following display shows sample IP trace output when a destination host name has been specified:
cs# trace ip ABA.NYC.mil
Type escape sequence to abort.
Tracing the route to ABA.NYC.mil (26.0.0.73)
1 DEBRIS.CISCO.COM (131.108.1.6) 1000 msec 8 msec 4 msec
2 BARRNET-GW.CISCO.COM (131.108.16.2) 8 msec 8 msec 8 msec
3 EXTERNAL-A-GATEWAY.STANFORD.EDU (192.42.110.225) 8 msec 4 msec 4 msec
4 BB2.SU.BARRNET.NET (131.119.254.6) 8 msec 8 msec 8 msec
5 SU.ARC.BARRNET.NET (131.119.3.8) 12 msec 12 msec 8 msec
6 MOFFETT-FLD-MB.in.MIL (192.52.195.1) 216 msec 120 msec 132 msec
7 ABA.NYC.mil (26.0.0.73) 412 msec 628 msec 664 msec
Table 5-34 describes the fields shown in the display.
| Field | Description |
|---|---|
1 | Indicates the sequence number of the communication server in the path to the host. |
DEBRIS.CISCO.COM | Host name of the communication server. |
131.108.1.61 | IP address of the communication server. |
1000 msec 8 msec 4 msec | Round-trip time for each of the three probes that are sent. |
Table 5-35 describes the characters that can appear in trace output.
| Char | Description |
|---|---|
nn msec | For each node, the round-trip time in milliseconds for the specified number of probes. |
* | The probe timed out. |
? | Unknown packet type. |
Q | Source quench. |
P | Protocol unreachable. |
N | Network unreachable. |
U | Port unreachable. |
H | Host unreachable. |
trace (privileged)
Use the trace privileged EXEC command to discover the routes the communication server's packets will actually take when traveling to their destination.
trace [protocol] [destination]
protocol | (Optional) The only protocol currently supported is ip. |
destination | (Optional) Destination address or host name on the command line. The default parameters for the appropriate protocol are assumed and the tracing action begins. |
The protocol argument is based on the communication server's examination of the format of destination. For example, if the communication server finds a destination in IP format, the protocol defaults to ip.
Privileged EXEC
The trace command works by taking advantage of the error messages generated by communication servers when a datagram exceeds its time-to-live (TTL) value.
The trace command starts by sending probe datagrams with a TTL value of one. This causes the first communication server to discard the probe datagram and send back an error message. The trace command sends several probes at each TTL level and displays the round-trip time for each.
The trace command sends out one probe at a time. Each outgoing packet may result in one or two error messages. A time exceeded error message indicates that an intermediate communication server has seen and discarded the probe. A destination unreachable error message indicates that the destination node has received the probe and discarded it because it could not deliver the packet. If the timer goes off before a response comes in, trace prints an asterisk (*).
The privileged-level trace command differs from the user-level trace command in that you can use nondefault parameters and invoke an extended trace test by entering the command without a destination argument. You will be stepped through a dialog to select the desired parameters.
Due to bugs in the IP implementation of various hosts and communication servers, the IP trace command might behave in odd ways.
Not all destinations will respond correctly to a probe message by sending back an ICMP port unreachable message. A long sequence of TTL levels with only asterisks, terminating only when the maximum TTL has been reached, might indicate this problem.
There is a known problem with the way some hosts handle an ICMP TTL exceeded message. Some hosts generate an ICMP message but they reuse the TTL of the incoming packet. Because this is zero, the ICMP packets do not make it back. When you trace the path to such a host, you might see a set of TTL values with asterisks (*). Eventually the TTL gets high enough that the ICMP message can get back. For example, if the host is six hops away, trace will time out on responses 6 through 11.
The following display shows sample IP trace output when a destination host name has been specified:
cs# trace ABA.NYC.mil
Type escape sequence to abort.
Tracing the route to ABA.NYC.mil (26.0.0.73)
1 DEBRIS.CISCO.COM (131.108.1.6) 1000 msec 8 msec 4 msec
2 BARRNET-GW.CISCO.COM (131.108.16.2) 8 msec 8 msec 8 msec
3 EXTERNAL-A-GATEWAY.STANFORD.EDU (192.42.110.225) 8 msec 4 msec 4 msec
4 BB2.SU.BARRNET.NET (131.119.254.6) 8 msec 8 msec 8 msec
5 SU.ARC.BARRNET.NET (131.119.3.8) 12 msec 12 msec 8 msec
6 MOFFETT-FLD-MB.in.MIL (192.52.195.1) 216 msec 120 msec 132 msec
7 ABA.NYC.mil (26.0.0.73) 412 msec 628 msec 664 msec
Table 5-36 describes the fields shown in the display.
| Field | Description |
|---|---|
1 | Indicates the sequence number of the communication server in the path to the host. |
DEBRIS.CISCO.COM | Host name of the communication server. |
131.108.1.6 | IP address of the communication server. |
1000 msec 8 msec 4 msec | Round-trip time for each of the three probes that are sent. |
The following display shows a sample trace session involving the extended dialog of the trace command.
cs# trace
Protocol [ip]:
Target IP address: mit.edu
Source address:
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to MIT.EDU (18.72.2.1)
1 ICM-DC-2-V1.ICP.NET (192.108.209.17) 72 msec 72 msec 88 msec
2 ICM-FIX-E-H0-T3.ICP.NET (192.157.65.122) 80 msec 128 msec 80 msec
3 192.203.229.246 540 msec 88 msec 84 msec
4 T3-2.WASHINGTON-DC-CNSS58.T3.ANS.NET (140.222.58.3) 84 msec 116 msec 88 msec
5 T3-3.WASHINGTON-DC-CNSS56.T3.ANS.NET (140.222.56.4) 80 msec 132 msec 88 msec
6 T3-0.NEW-YORK-CNSS32.T3.ANS.NET (140.222.32.1) 92 msec 132 msec 88 msec
7 T3-0.HARTFORD-CNSS48.T3.ANS.NET (140.222.48.1) 88 msec 88 msec 88 msec
8 T3-0.HARTFORD-CNSS49.T3.ANS.NET (140.222.49.1) 96 msec 104 msec 96 msec
9 T3-0.ENSS134.T3.ANS.NET (140.222.134.1) 92 msec 128 msec 92 msec
10 W91-CISCO-EXTERNAL-FDDI.MIT.EDU (192.233.33.1) 92 msec 92 msec 112 msec
11 E40-RTR-FDDI.MIT.EDU (18.168.0.2) 92 msec 120 msec 96 msec
12 MIT.EDU (18.72.2.1) 96 msec 92 msec 96 msec
Table 5-37 describes the fields that are unique to the extended trace sequence, as shown in the display.
| Field | Description |
|---|---|
Target IP address | You must enter a host name or an IP address. There is no default. |
Source address | One of the interface addresses of the communication server to use as a source address for the probes. The communication server will normally pick what it feels is the best source address to use. |
Numeric display | The default is to have both a symbolic and numeric display; however, you can suppress the symbolic display. |
Timeout in seconds | The number of seconds to wait for a response to a probe packet. The default is 3 seconds. |
Probe count | The number of probes to be sent at each TTL level. The default count is 3. |
Minimum Time to Live [1] | The TTL value for the first probes. The default is 1, but it can be set to a higher value to suppress the display of known hops. |
Maximum Time to Live [30] | The largest TTL value that can be used. The default is 30. The trace command terminates when the destination is reached or when this value is reached. |
Port Number | The destination port used by the UDP probe messages. The default is 33434. |
Loose, Strict, Record, Timestamp, Verbose | IP header options. You can specify any combination. The trace command issues prompts for the required fields. Note that trace will place the requested options in each probe; however, there is no guarantee that all communication servers (or end nodes) will process the options. |
Loose | Allows you to specify a list of nodes that must be traversed when going to the destination. |
Strict | Allows you to specify a list of nodes that must be the only nodes traversed when going to the destination. |
Record | Allows you to specify the number of hops to leave room for. |
Timestamp | Allows you to specify the number of time stamps to leave room for. |
Verbose | If you select any option, the verbose mode is automatically selected and trace prints the contents of the option field in any incoming packets. You can prevent verbose mode by selecting it again, toggling its current setting. |
Table 5-38 describes the characters that can appear in trace output.
| Char | Description |
|---|---|
nn msec | For each node, the round-trip time in milliseconds for the specified number of probes. |
* | The probe timed out. |
? | Unknown packet type. |
Q | Source quench. |
P | Protocol unreachable. |
N | Network unreachable. |
U | Port unreachable. |
H | Host unreachable. |
trace (user)
To establish a username-based authentication system at login, even though your network cannot support a TACACS service, use the username global configuration command.
username name [nopassword | password encryption-type password]
name | Host name, server name, user ID, or command name. |
nopassword | (Optional) No password is required for this user to log in. This is usually most useful in combination with the autocommand keyword. |
password | Specifies a possibly encrypted password for this username. |
encryption-type | (Optional) A single-digit number that defines whether the text immediately following is encrypted, and, if so, what type of encryption is used. Currently defined encryption types are 0, which means that the text immediately following is not encrypted, and 7, which means that the text is encrypted using a Cisco-defined encryption algorithm. |
password | (Optional) A password can contain embedded spaces and must be the last option specified in the username command. |
secret | For CHAP authentication: specifies the secret for the local communication server or the remote device. The secret is encrypted when it is stored on the local communication server. This prevents the secret from being stolen. The secret can consist of any string of up to 11 printable ASCII characters. There is no limit to the number of username/password combinations that can be specified, allowing any number of remote devices to be authenticated. |
access-class | (Optional) Specifies an outgoing access list that overrides the access list specified in the access-class line configuration command. It is used for the duration of the user's session. |
number | (Optional) The access list number. |
autocommand | (Optional) Causes the specified command to be issued automatically after the user logs in. When the command is complete, the session is terminated. As the command can be any length and contain imbedded spaces, commands using the autocommand keyword must be the last option on the line. |
command | (Optional) The command string. |
noescape | (Optional) Prevents a user from using an escape character on the host to which that user is connected. |
nohangup | (Optional) Prevents the communication server from disconnecting the user after an automatic command (set up with the autocommand keyword) has completed. Instead, the user gets another login prompt. |
None
Global configuration
The username command provides username/password authentication for login purposes only. (Note that it does not provide username/password authentication for enable mode when the enable use-tacacs command is also used.)
Multiple username commands can be used to specify options for a single user.
Add a username entry for each remote system that the local communication server communicates with and requires authentication from. The remote device must have a username entry for the local communication server. This entry must have the same password as the local communication server's entry for that remote device.
This command can be useful for defining usernames that get special treatment, for example, an "info" username that does not require a password, but connects the user to a general purpose information service.
The username command is also required as part of the configuration for the Challenge Handshake Authentication Protocol (CHAP). For each remote system that the local communication server communicates with from which it requires authentication, add a username entry.
The keyword noescape prevents users from using escape characters on the hosts to which they are connected.
To implement a service similar to the UNIX who command, which can be entered at the login prompt and lists the current users of the communication server, the username command takes the following form:
username who nopassword nohangup autocommand show users
To implement an information service that does not require a password to be used, the command takes the following form:
username info nopassword noescape autocommand telnet nic.ddn.mil
To implement an ID that will work even if the TACACS servers all break, the command takes the following form:
username superuser password superpassword
The following example configuration enables CHAP on serial interface 0. It also defines a password for the local server, Adam, and a remote server, Eve.
hostname Adam
interface serial 0
encapsulation ppp
ppp authentication chap
username Adam password oursystem
username Eve password theirsystem
When you look at your configuration file, the passwords will be encrypted and the display will look similar to the following:
hostname Adam
interface serial 0
encapsulation ppp
ppp authentication chap
username Adam password 7 1514040356
username Eve password 7 121F0A18
hostname
Posted: Mon Oct 21 12:25:33 PDT 2002
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