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This chapter describes the basic tasks that can be completed to manage the general system (nonprotocol-specific) features. Our system management features are supported via the Simple Network Management Protocol (SNMP). This chapter describes the tasks needed to configure SNMP support on the communication server. A part of SNMP is the Management Information Base (MIB). MIBs provide variables that can be set or read to change parameters or provide information on network devices and interfaces. Cisco supports several MIBs, including the Internet standard MIB II, and also provides its own Cisco MIB. For information on the Cisco MIB, see the Cisco Management Information Base (MIB) User Quick Reference.
For a list of recommended books on network management, refer to the appropriate appendix in the Communication Server Command Reference publication.
For a complete description of the commands mentioned in this chapter, refer to of the Communication Server Command Reference publication.
In general, you will be performing the following types of system or network management:
The following sections describe how to perform these tasks.
The configuration of network devices determines the network's behavior. To manage device configurations, you need to list and compare configuration files on running devices, store configuration files on network servers for shared access, and perform software installations and upgrades.
You can complete any of the following tasks to perform configuration management functions:
The following sections summarize these tasks.
One of the first basic tasks is to name your communication server. The name of the communication server is considered the host name and is the name that is displayed by the system prompt. If no name is configured, the system default communication server name is cs. You can set the communication server to the name of your choice while in global configuration mode as follows:
| Task | Command |
|---|---|
| Set the host name. | hostname name |
Communications server products provide an array of time-of-day services. These services allow the products to keep track of the current time and date to a high degree of accuracy, to synchronize multiple products to the same time, and to provide time services to other systems.
The heart of the time service is the system clock. This clock, which is always running from the moment the system starts up, keeps track of the current date and time. The system clock can be set from a number of sources, and can in turn be used to distribute the current time through various mechanisms to other systems. When the system is initialized, the system clock is set to midnight on March 1, 1993. The system clock can then be set using the following methods:
The system clock can provide time to the following services:
The system clock internally keeps track of time based on Coordinated Universal Time (UTC), also known as Greenwich Mean Time (GMT). You can configure information about the local time zone and summer time (daylight savings time) so that the time is displayed correctly relative to the local time zone.
The system clock keeps track of whether the time is "authoritative" or not (that is, whether it has been set by a time source considered to be authoritative). If it is not authoritative, the time will be available only for display purposes and will not be redistributed.
The Network Time Protocol (NTP) is a protocol designed to time-synchronize a network of machines. NTP runs over UDP, which in turn runs over IP. NTP is documented in RFC 1305.
An NTP network usually gets its time from an authoritative time source, such as a radio clock or an atomic clock attached to a time server. NTP is then used to distribute this time across the network. NTP is extremely efficient; no more than one packet per minute is necessary to synchronize two machines to within a millisecond of one another.
NTP uses the concept of a "stratum" to describe how many NTP "hops" away a machine is from an authoritative time source. A "stratum 1" time server has a radio or atomic clock directly attached, a "stratum 2" time server receives its time via NTP from a "stratum 1" time server, and so on. A machine running NTP will automatically choose as its time source the machine with the lowest stratum number that it is configured to communicate with via NTP. This strategy effectively builds a self-organizing tree of NTP speakers.
NTP is careful to avoid synchronizing to a machine whose time may not be accurate. It avoids doing so in two ways. First of all, NTP will never synchronize to a machine that is not in turn synchronized itself. Secondly, NTP will compare the time reported by several machines, and will not synchronize to a machine whose time is significantly different than the others, even if its stratum is lower.
The communications between machines running NTP (known as "associations") are usually statically configured; each machine is given the IP address of all machines with which it should form associations. Accurate timekeeping is made possible by exchanging NTP messages between each pair of machines with an association. However, in a LAN environment, NTP may be configured to use IP broadcast messages instead. This alternative reduces configuration complexity, because each machine can simply be configured to send or receive broadcast messages. However, the accuracy of timekeeping is marginally reduced, because the information flow is one-way only.
The time kept on a machine is a critical resource, so it is strongly recommended that the security features of NTP be used to avoid the accidental or malicious setting of incorrect time. Two mechanisms are available: an access list-based restriction scheme and an encrypted authentication mechanism.
Our implementation of NTP does not support stratum 1 service; in other words, it is not possible to connect a radio or atomic clock to this communication server. It is recommended that time service for your network be derived from the public NTP servers available in the IP Internet. If the network is isolated from the Internet, our implementation of NTP allows a machine to be configured so that it acts as though it is synchronized via NTP, when in fact it has determined the time using other means. Other machines will then synchronize to that machine via NTP.
NTP software for host systems is included by a number of manufacturers, and a publicly available version for systems running UNIX and its various derivatives is also available. This software allows host systems to be time-synchronized as well.
If no other source of time is available, the current time and date can be manually configured after the system is restarted. The time will remain accurate until the next system restart. It is recommended that manual configuration be used only as a last resort.
To set up time services manually, complete the following tasks. If you have an outside source to which the communication server can synchronize, you do not need to manually set the system clock.
Complete the following task in global configuration mode to configure the time zone used by the communication server:
| Task | Command |
|---|---|
| Set the communication server time zone. | clock timezone name hours [minutes] |
To configure summer time (daylight savings time) in areas where it starts and ends on a particular day of the week each year, use the following form of the command in global configuration mode:
| Task | Command |
|---|---|
| Configure summer time using the same day of the week each year. | clock summer-time name recurring [week day month hh:mm week day month hh:mm] [offset] |
If summer time in your area does not follow this pattern, you can configure the exact date and time of the next summer time events using one of the following commands in global configuration mode:
| Task | Command |
|---|---|
| Configure summer time using exact date and time. | clock summer-time name date month day year hh:mm month day year hh:mm [offset]
or clock summer-time name date day month year hh:mm day month year hh:mm [offset] |
If you have an outside source on the network that provides time services (such as an NTP server service), you do not need to manually set the system clock.
However, if you have do not have any time service source, complete one of the following tasks in EXEC mode to set the system clock:
| Task | Command |
|---|---|
| Set the system clock. | clock set hh:mm:ss day month year
or clock set hh:mm:ss month day year |
If you want to establish very accurate time synchronization among the machines in your network, configure the Network Time Protocol (NTP). There are a number of subtasks to perform:
If you want to authenticate the associations with other systems for security purposes, perform the tasks that follow. The first task enables the NTP authentication feature. The second task defines each of the authentication keys. Each key has a key number, a type, and a value. Currently the only key type supported is "md5." Third, a list of "trusted" authentication keys is defined. If a key is trusted, then this system will be willing to synchronize to a system that uses this key in its NTP packets.
To configure NTP authentication, perform the following tasks in global configuration mode:
If you want to form an NTP association with another system, perform one of the tasks in global configuration mode:
The association can be a peer association (meaning that this communication server is willing to either synchronize to the other system or to allow the other system to synchronize to it), or it can be a server association (meaning that this communication server will only synchronize to the other system, and not the other way around). Note that only one end of an association needs to be configured; the other system will automatically establish the association.
The system can either send broadcast packets or listen to them on an interface-by-interface basis. The estimated round-trip delay for broadcast packets can also be configured. Perform one or more of these tasks in global configuration mode if you want to use NTP's broadcast feature:
| Task | Command |
|---|---|
| Send NTP broadcast packets. | ntp broadcast [version number][key nn] |
| Receive NTP broadcast packets. | ntp broadcast client |
| Adjust estimated delay. | ntp broadcastdelay microseconds |
You can control NTP access on two levels by completing the following tasks:
To control access to NTP services, you can create an NTP access group and apply a basic IP access list to it. To do so, perform the following task in global configuration mode:
| Task | Command |
|---|---|
| Create an access group and apply a basic IP access list to it. | ntp access-group {query-only | serve-only | serve | peer} number |
The access group options are scanned in the following order from least restrictive to most restrictive:
If the source IP address matches the access lists for more than one access type, the first type is granted.
If no access groups are specified, all access types are granted to all systems. If any access groups are specified, only the specified access types will be granted.
For details on NTP control queries, see RFC 1305 (NTP version 3).
NTP services are enabled on all interfaces by default. You can disable NTP packets from being received through an interface by performing the following task in interface configuration mode:
| Task | Command |
|---|---|
| Disable NTP services on a specific interface. | ntp disable |
When the system sends an NTP packet, the source IP address is normally set to the address of the interface through which the NTP packet is sent. Perform the following task in global configuration mode if you want to configure a specific interface from which the IP source address will be taken:
| Task | Command |
|---|---|
| Configure an interface from which the IP source address will be taken. | ntp source interface |
This interface will be used for the source address for all packets sent to all destinations. If a source address is to be used for a specific association, use the source parameter on the ntp peer or ntp server command.
Perform the following task in global configuration mode if you want the system to be an authoritative NTP server, even if the system is not synchronized to an outside time source:
| Task | Command |
|---|---|
| Make the system an authoritative NTP server. | ntp master [stratum] |
You can monitor clock, calendar, and NTP EXEC services by completing the following tasks in EXEC mode:
| Task | Command |
|---|---|
| Display the current system clock time. | show clock [detail] |
| List NTP statistics. | show ntp associations [detail]
or |
The Simple Network Management Protocol (SNMP) provides a way for network management client and server applications to communicate. It does this by providing a message format for sending information between an SNMP manager and an SNMP agent.
The SNMP agent contains Management Information Base (MIB) variables that the SNMP manager can request or change. The SNMP agent can also send traps, or messages alerting the SNMP manager to a condition on the network. Traps can indicate improper user authentication, restarts, link status (up or down), closing of a TCP connection, or loss of connection to a neighbor communication server.
Our implementation of SNMP supports all MIB II variables (as described in RFC 1213 and SNMP traps (as described in RFC 1215). Cisco also supports the definition of management information described in RFCs 1155, 1157, and 1213, and supports some or all variables in the MIBs described in the following RFCs: 1156, 1212, 1231, 1285, 1286, 1315, 1381, and 1382.
Cisco also provides its own MIB with every system. With the current software release, the Cisco MIB provides a new chassis MIB variable that enables the SNMP manager to gather data on system card descriptions, serial numbers, hardware and software revision levels, and slot locations.
See the Cisco Management Information Base (MIB) User Quick Reference for a detailed description of each Cisco MIB variable and SNMP trap.
You can perform the following tasks to configure SNMP support on the communication server:
These tasks are described in the following sections.
You can enable SNMP server operation and specify which hosts can send requests to the communication server by performing the following tasks in global configuration mode:
The SNMP trap operations allow a system administrator to configure the communication server to send information to a network management application when a particular event occurs. You can specify the following features for SNMP server trap operations:
Perform the following tasks in global configuration mode, as needed, to define traps for your system configuration:
You can set the maximum packet size permitted when the SNMP server is receiving a request or generating a reply. To do so, perform the following task in global configuration mode:
| Task | Command |
|---|---|
| Establish the maximum packet size. | snmp-server packetsize bytes |
Using SNMP packets, a network management tool can send messages to users on virtual terminals and the console. This facility operates in a similar fashion to the EXEC send command; however, the SNMP request that causes the message to be issued to the users also specifies the action to be taken after the message is delivered. One possible action is a shutdown request. Because the ability to cause a reload from the network is a powerful feature, you can perform the following task in global configuraiton mode to protect it is protected by this global configuration command:
| Task | Command |
|---|---|
| Requests that a shutdown occur after a message is delivered from a network management tool. | snmp-server system-shutdown |
To understand how to use this feature with SNMP requests, read the document mib.txt available by anonymous ftp from ftp.cisco.com.
You can set the system contact, location, and serial number of the SNMP server so that these descriptions can be accessed via the configuration file. To do so, perform the following tasks in global configuration mode:
| Task | Command |
|---|---|
| Set the system contact string. | snmp-server contact text |
| Set the system location string. | snmp-server location text |
| Set the system serial number. | snmp-server chassis-id text |
Once the SNMP server has been enabled with the snmp-server community command, you can specifically disable it by performing the following task in global configuration mode:
| Task | Command |
|---|---|
| Disable SNMP server operation. | no snmp-server |
To monitor SNMP input and output statistics, including the number of illegal community string entries, errors, requested variables, and so on, complete the following task in EXEC mode:
| Task | Command |
|---|---|
| Monitor SNMP status. | show snmp |
To manage security on the network, you need to restrict access to the system. You can do so on several different levels. You can assign passwords (and encrypt them) to restrict access to communication server terminal lines, login connections, or privileged EXEC mode. You can establish Terminal Access Controller Access Control System (TACACS) protection for network servers that have shared access, and you can create access lists to filter traffic to and from specific destinations. You can also restrict login connections to specific users with user authentication support.
To set up security features, you need to identify sensitive information, find the network access points to that information, secure these access points, and maintain the secure access points.
This section describes the following tasks used to control access to the system:
Other chapters in this guide provide information on protocol-specific security features.
Complete the following tasks to establish password protection:
You can provide access control on a terminal line by entering the password and establishing password checking. To do so, perform the following tasks in line configuration mode:
| Task | Command |
|---|---|
| Step 1 Assign a password to a terminal or other device on a line. | password text |
| Step 2 Enable password checking. | login |
The login and password commands are documented further in the"Line Configuration and Terminal Setting Commands" chapter in the Communication Server Command Reference.
The password checker is case sensitive. The password Secret is different than the password secret, for example, and the password two words is an acceptable password.
You can control access to the system by setting a password that must be entered to gain access to the privileged EXEC mode, and therefore to the system configuration. Perform the following task in global configuration mode:
| Task | Command |
|---|---|
| Establish a password for the privileged EXEC mode. | enable password password |
You can increase access security to your communication server by configuring the communication server to encrypt passwords, because protocol analyzers can examine packets. Encryption prevents the password from being visible in the configuration file.
Configure the communication server to encrypt passwords by performing the following task in global configuration mode:
| Task | Command |
|---|---|
| Encrypt a password. | service password-encryption |
It is not possible to recover a lost encrypted password.
You can disable line password verification by disabling password checking. To do so, perform the following task in line configuration mode:
| Task | Command |
|---|---|
| Disable password checking or allow access to a line without password verification. | no login |
If your server has the nonvolatile memory option, you can accidentally lock yourself out if you enable password checking on the console terminal line and then forget the line password.
To recover a lost password on the ASM-CS, force the server into factory diagnostic mode and then follow these steps:
Step 1 You will be asked if you want to set the manufacturers' addresses. Respond by typing Yes. You will then see the following prompt:
Step 2 Type the enable command to get the privileged prompt:
enable
Step 3 Type the show configuration command to review the system configuration and find the password. Do not change anything in the factory diagnostic mode.
show configuration
Step 4 To resume normal operation, restart the server and/or reset the configuration register.
Step 5 Log into the server with the password that was shown in the configuration file.
Unplug the 500-CS. Hold down the Reset button while plugging the power cord back in., and keep holding it down for at least three seconds after the "PWR" (power) LED comes on.
This section summarizes the types of access lists that you can create to control access at the packet level. This summary provides a brief description of access lists in alphabetical order by protocol.
You can control access to lines and interfaces by completing the following tasks:
Step 1 Create an access list based upon particular restrictions.
Step 2 Assign an access list to a specific interface.
Table 1-1 provides a summary of access list ranges.
| Protocol | Range |
|---|---|
| IP | 1-99 |
| Extended IP | 100-199 |
| Ethernet type code | 200-299 |
| Ethernet address | 700-799 |
| Novell | 800-899 |
| Extended Novell | 900-999 |
| Novell SAP | 1000-1099 |
You can assign access lists to DDR interfaces by performing the following tasks:
For more information about dial-on-demand (DDR) routing see the chapter"Configuring Dial-on-Demand Routing."
You can create the following types of IP access lists:
You can create a standard IP access list based on the address mask by completing the following task:
| Task | Command |
|---|---|
| Set address masks restrictions. | access-list 1-99 {permit | deny} source source-mask |
You can assign a standard IP access list to a specified interface or line by performing these tasks:
You can assign extended IP access lists to a specified interface or line by performing these tasks:
| Task | Command |
| Define an extended access list. | access-list 100-199 {permit | deny ip | tcp | udp | icmp | igrp} source source-mask dest dest-mask [lt | gt | eq | neq dest-port][established] |
| Apply an access list to an interface. | ip access-group 100-199 {out | in} |
For more information about IP, see the IP routing chapter.
You can create several types of IPX access lists to restrict access based on source and destination address and mask, IPX protocol, name, and byte pattern. Perform the appropriate tasks from the following list to do so:
You can create several types of IPX filters by applying access lists to individual interfaces by performing the following tasks:
For more information about configuring Novell IPX, see the chapter"Configuring Novell IPX."
You can configure the communication server to use a special TCP/IP protocol called Terminal Access Controller Access Control System (TACACS). TACACS provides an additional level of control over servers running on a timesharing system. The Defense Data Network (DDN) developed TACACS to control access to its TAC servers; Cisco patterned its TACACS support after the DDN application.
You can establish TACACS password protection on both user and privileged levels of the system EXEC. The TACACS security program allows you to set these features:
The following sections describe these tasks.
You can enable password checking at login by performing the following task in line configuration mode:
| Task | Command |
|---|---|
| Set the TACACS-style user ID and password checking mechanism. | login tacacs |
The login tacacs command is documented further in the chapter"Line Configuration and Terminal Setting Commands," in the Communication Server Command Reference.
You can disable password checking at the user level and guarantee forced login by performing the following task in global configuration mode:
| Task | Command |
|---|---|
| Set "last resort" options for logins. | tacacs-server last-resort {password | succeed} |
You can specify that the first TACACS request to a TACACS server be made without password verification, perform the following task in global configuration mode:
| Task | Command |
|---|---|
| Set TACACS password as optional. | tacacs-server optional-passwords |
You can enable the use of TACACS to determine whether a user can access the privileged command level by performing the following task in global configuration mode:
| Task | Command |
|---|---|
| Set the TACACS-style user ID and password checking mechanism at the privileged command level. | enable use-tacacs |
You can specify what happens if the TACACS server does not respond by performing the following task in global configuration mode:
| Task | Command |
|---|---|
| Set "last resort" options for logins at the privileged prompt. | enable last-resort {succeed | password} |
You can cause a message to be transmitted to the TACACS server with retransmission being performed by a background process by performing the following task in global configuration mode:
| Task | Command |
|---|---|
| Set server notification of user actions. | tacacs-server notify {connection | enable | logout} |
For a TCP connection, you can specify that if a user tries to make a connection, the communication server requires a response from the network or communication server indicating whether the user can make the connection. You can also specify that the communication server should perform authentication even when a user is not logged in.
For a SLIP or PPP session, you can specify that if a user tries to start a session, the communication server requires a response from the network or communication server indicating whether the user can start the session. You can specify that the communication server should perform authentication even when a user is not logged in. You can also request that the communication server install access lists.
For use of the enable command, you can specify that if a user issues the enable command, the communication server must respond indicating whether the user can give the command.
To configure any of these scenarios, perform the following task in global configuration mode:
| Task | Command |
|---|---|
| Set server authentication of user actions. | tacacs-server authenticate {connection [always] | enable | slip [always] [access-lists]} |
The tacacs-server authenticate command is only available when you have set up an extended TACACS server using the latest Cisco extended TACACS server software, available using FTP (see the README file in the ftp.cisco.com directory).
You can specify the names of the IP host or hosts maintaining a TACACS server. The software searches for the hosts in the order specified, so this feature can be useful for setting up a list of preferred servers.
You can also modify the number of times the system software searches the list of TACACS servers and the interval it waits for a reply.
Perform the following tasks in global configuration mode, as needed, for your system configuration:
You can set controls on the number of login attempts that can be made on a line set up for TACACS by performing the following task in global configuration mode:
| Task | Command |
|---|---|
| Control the number of login attempts that can be made on a line set for TACACS verification. | tacacs-server attempts count |
Extended TACACS mode provides information about the terminal requests to help set up UNIX auditing trails and accounting files for tracking use of protocol translators, communication servers, and communication servers. The information includes responses from these network devices and validation of user requests.
An unsupported, extended TACACS server is available from Cisco Systems using ftp for UNIX users who want to create the auditing programs (see the README file in the ftp.cisco.com directory).
Extended TACACS differs from standard TACACS in that standard TACACS provides only username and password information.
To enable extended TACACS mode, perform the following task in global configuration mode:
| Task | Command |
|---|---|
| Enable an extended TACACS mode. | tacacs-server extended |
You can create a username-based authentication system. This can be useful for the following reasons:
Perform the following tasks in global configuration mode, as needed for your system configuration:
The keyword noescape prevents users from using escape characters on the hosts to which they are connected.
Access control using Challenge Handshake Authentication Protocol (CHAP) is available on all serial interfaces configured for PPP encapsulation. The authentication feature reduces the risk of security violations on your communication server.
When CHAP is enabled, a remote device (a PC, workstation, or communication server) attempting to connect to the local communication server is requested, or "challenged," to respond. The challenge consists of a random number and the host name of the local communication server. This challenge is transmitted to the remote device. The required response is an encrypted version of a secret password, or "secret," plus the host name of the remote device. The remote device verifies the secret by looking up the host name that was received in the challenge. When the local communication server receives the challenge response, it verifies the secret by looking up the name of the remote device given in the response. The secret passwords must be identical on the remote device and the local communication server.
By transmitting this encrypted response, the secret is never transmitted, thus preventing other devices from stealing it and gaining illegal access to the system. Without the proper response, the remote device cannot connect to the local communication server.
CHAP transactions occur only when a link is established. The local communication server does not request a password during the rest of the call. (The local communication server can, however, respond to such requests from other devices during a call.)
To use CHAP, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
| Enable CHAP on the interface. | ppp authentication chap |
CHAP is specified in RFC 1334. It is an additional authentication phase of the PPP Link Control Protocol.
Once you have enabled CHAP, the local communication server requires a password from remote devices. If the remote device does not support CHAP, no traffic is passed to that device.
For more information about CHAP and PPP see the"Configuring Interfaces" chapter and
the chapter"Configuring SLIP and PPP."
Access control using the Password Authentication Protocol (PAP) is available on all serial interfaces. The authentication feature reduces the risk of security violations on your communication server.
To use PAP, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
| Enable PAP on the interface. | ppp authentication pap |
To manage network faults, you need to discover, isolate, and fix the problems. You can discover problems with the system's monitoring commands, isolate problems with the system's test commands, and resolve problems with other commands, including the debug command.
This section introduces basic fault management commands. For detailed troubleshooting procedures and a variety of scenarios, see the Troubleshooting Internetworking Systems publication. For complete detail on all debug commands, see the Debug Command Reference publication.
To perform general fault management, complete the following tasks:
Most chapters in this guide include fault management tasks listed under a monitoring and maintaining section.
To provide information about system processes, the software includes an extensive list of EXEC commands that begin with the word show and, when executed, display detailed tables of system information. Following is a list of the more common system management show commands. Perform these tasks in EXEC mode to display the information described:
| Task | Command |
|---|---|
| Display information about all active processes. | show processes [cpu | memory] |
| Display the configured protocols. | show protocols |
Look for specific show commands in the tables of configuration tasks found throughout the chapters in this guide. See the Communication Server Command Reference publication for detailed descriptions of the commands.
The following sections describe the EXEC commands you can use to monitor and troubleshoot the voltage and temperature of your system environment.
Complete the following tasks to test basic network connectivity:
The TCP keepalive capability allows a communication server to detect when the host with which it is communicating experiences a system failure, even if data stops being transmitted (in either direction). This is most useful on incoming connections. For example, if a host failure occurs while talking to a printer, the communication server might never notice, since the printer does not generate any traffic in the opposite direction. If keepalives are enabled, they are sent once every minute on otherwise idle connections. If five minutes pass and no keepalives are detected, the connection is closed. The connection will also be closed if the host replies to a keepalive packet with a reset packet. This will happen if the host crashes and comes back up again.
To set up the TCP keepalive packet service, perform the following task in global configuration mode:
As an aid to diagnosing basic network connectivity, many network protocols support an echo protocol. The protocol involves sending a special datagram to the destination host, then waiting for a reply datagram from that host. Results from this echo protocol can help in evaluating the path-to-host reliability, delays over the path, and whether the host can be reached or is functioning.
To use the echo protocol, perform the following task in either user EXEC or privileged EXEC mode:
| Task | Command |
|---|---|
| Invoke a diagnostic tool for testing connectivity. | ping [protocol] {host | address} |
Look for specific ping commands in the tables of configuration tasks found throughout the chapters in this guide. See the Communication Server Command Reference publication for detailed descriptions of the command.
You can discover the routes IP packets will actually take when traveling to their destination. To do so, perform one of the following tasks:
Trace packet routes through the network (privileged level). | trace [destination] |
| Trace packet routes through the network (user level). | trace ip destination |
You can limit TCP transactions by performing the following task in global configuration mode:
| Task | Command |
|---|---|
| Enable the Nagle slow packet avoidance algorithm. RFC 896. | service nagle |
You can convert the line numbers on the ASM-CS communication server from their default octal to a decimal number.
| Task | Command |
|---|---|
| Specify that line numbers be displayed and interpreted as decimal numbers rather than octal numbers. | service decimal-tty |
You can test the status of the following items:
By default, the network servers send the output from the EXEC command debug and system error messages to the console terminal. You can redirect these messages, as well as output from asynchronous events such as interface transition, to other destinations. These destinations include virtual terminals, internal buffers, and UNIX hosts running a syslog server; the syslog format is compatible with 4.3 BSD UNIX.
Additionally, you can set the severity level of the messages to control the type of messages displayed. You can also have log messages timestamped to enhance real-time debugging and management.
With the current software release, there are three new syslog messages at LOG_NOTICE syslog level that make it easier to check the status of how the system provides address resolution. An example follows:
%LINK-5-BOOTP: Ethernet0 address 131.108.160.24, resolved by 131.108.1.111
%LINK-5-RARP: Ethernet0 address 131.108.160.24, resolved by 131.108.1.111
%LINK-5-SLARP: Ethernet0 address 131.108.160.24, resolved by 131.108.1.111
There are also new startup messages that help you identify NVRAM problems:
Warning: NVRAM device not found
Warning: NVRAM invalid, possibly due to write erase
The following level 4 LOG_WARNING message has been added for FDDI status information:
%FDDISTAT-4-STATUS: FDDI state indication detected on interface variable
The possible values for indication are listed in the next paragraph. The variable will be replaced with something like fddi0, for example.
Changes in status reflect interface connectivity or cabling problems (or fixes). The possible status reports include the following indications:
isolated
wrap A
wrap B
wrap a-B
thru A
thru B
thru A-B
To set up the syslog daemon on a 4.3 BSD UNIX system, include a line such as the following in the file /etc/syslog.conf:
local7.debugging /usr/adm/logs/cisco.log
The local7 keyword specifies the logging facility to be used; this can be changed.
The debugging argument specifies the syslog level. Refer to your syslog manual page.
The syslog daemon sends messages at or above this level to the file specified in the next field. The file must already exist, and the syslog daemon must have permission to write to it.
By default, error messages are directed to the system console. To direct messages to other devices, perform one of the following tasks in global configuration mode:
| Task | Command |
|---|---|
| Log messages to an internal buffer. | logging buffered |
| Log messages to a UNIX syslog server host. | logging host |
| Redirect messages to the system console. | no logging on |
To display system error messages to a nonconsole terminal, perform the following task in privileged EXEC mode
| Task | Command |
|---|---|
| Display system error message on a nonconsole terminal. | terminal monitor l |
The terminal monitor command is described further in the chapter"Line Configuration and Terminal Setting Commands," in the Communication Server Command Reference.
You can limit messages displayed to the selected device by specifying the severity level of the error message. To do so, perform one of the following tasks in global configuration mode:
| Task | Command |
|---|---|
| Limit messages logged to the console. | logging console level |
| Limit messages logged to the terminal lines. | logging monitor level |
| Limit messages logged to the syslog servers. | logging trap level |
Table 1-2 lists the error message levels and corresponding UNIX syslog definitions.
| Level Keyword | 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 |
Current software generates four categories of error messages:
The default is to log to the console messages at the debugging level and higher.
You can also configure the system log (syslog) facility in which error messages are sent by performing the following task in global configuration mode:
| Task | Command |
|---|---|
| Configure system log facilities. | logging facility facility-type |
Table 1-3 lists the logging facility types and their descriptions.
| Facility Type | Description |
| auth | Indicates the authorization system. |
| cron | Indicates the cron facility. |
| daemon | Indicates the system daemon. |
| kern | Indicates the Kernel. |
| local0-7 | Reserved for locally defined messages |
| lpr | Indicates line printer system. |
| Indicates mail system. | |
| news | Indicates USENET news. |
| sys9 | Indicates system use. |
| sys10 | Indicates system use. |
| sys11 | Indicates system use. |
| sys12 | Indicates system use. |
| sys13 | Indicates system use. |
| sys14 | Indicates system use. |
| syslog | Indicates the system log. |
| user | Indicates user process. |
| uucp | Indicates UNIX-to-UNIX copy system. |
To display the addresses and levels associated with the current logging setup, as well as any other logging statistics, perform the following task in EXEC mode:
| Task | Command |
| Display the state of syslog error and event logging, including host addresses and whether console logging is enabled. | show logging |
By default, log messages are not timestamped. You can enable timestamping of log messages by performing the following task in global configuration mode:
Your communication server includes hardware and software to aid in tracking down problems with the communication server or with other hosts on the network. The privileged debug EXEC commands start the console display of several classes of network events. The following tasks describe, in general, the system debug message feature. Refer to the Debug Command Reference publication for all information regarding debug commands. Also refer to the Troubleshooting Internetworking Systems publication.
You can configure timestamping of system debug messages. Timestamping enhances real-time debugging by providing the relative timing of logged events. This information is especially useful when customers send debugging output to your technical support personnel for assistance. To enable timestamping of system debug messages, perform the following task in global configuration mode:
Normally, the messages are displayed only on the console terminal. See the section "Set the Error Message Display Device" earlier in this chapter to change the output device.
To manage system performance, you need to monitor and determine response time, error rates, and availability. Once these factors are determined, you can perform load balancing and modify system parameters to enhance performance. For example, priority queuing allows you to prioritize traffic order.
This section describes how to manage general system performance by completing the following tasks:
Cisco provides two types of queuing strategies for prioritizing network traffic:
You can configure both priority queuing and custom queueing, but you can only assign either a priority group or a custom queue to an interface.
Priority output queuing is a mechanism that allows the administrator to set priorities on the type of traffic passing through the network. Packets are classified according to various criteria, including protocol and subprotocol type, and then queued on one of four output queues (high, medium, normal, and low).
When the server is ready to transmit a packet, it scans the priority queues in order, from highest to lowest, to find the highest priority packet. After that packet is completely transmitted, the server scans the priority queues again. If a priority output queue fills up, packets will be dropped and, for IP, quench indications will be sent to the original transmitter.
Although you can enable priority output queuing for any interface, the intended application was for low bandwidth, congested serial interfaces. The priority output queuing mechanism allows traffic control based on protocol or interface type. You can also set the size of the queue and defaults for what happens to packets that are not defined by priority output queue rules.
The priority output queuing mechanism can be used to manage traffic from all networking protocols. Additional fine-tuning is available for IP and for setting boundaries on the packet size.
The four priority queues--high, medium, normal, and low--are listed in order from highest to lowest priority. Keepalives sourced by the network server are always assigned to the high priority queue; all other management traffic (such as IGRP updates) must be configured. Packets that are not classified by the priority list mechanism are assigned to the normal queue.
A priority list is a set of rules that describes how packets should be assigned to priority queues. A priority list might also describe a default priority or the queue size limits of the various priority queues.
Priority queuing introduces a fairness problem in that packets classified to lower-priority queues may not get serviced in a timely manner, or at all, depending upon the bandwidth used by packets sent from the higher-priority output queues.
With custom output queuing, a "weighted fair" queuing strategy is implemented for the processing of interface output queues. You can control the percentage of an interface's available bandwidth that is used by a particular kind of traffic. When custom queuing is enabled on an interface, the system maintains 11 output queues for that interface that can be used to modify queueing behavior.
For queue numbers 1 through 10, the system cycles through the queues sequentially, delivering packets in the current queue before moving on to the next. Associated with each output queue is a configurable byte count, which specifies how many bytes of data the system should deliver from the current queue before it moves on to the next queue. When a particular queue is being processed, packets are sent until the number of bytes sent exceed the queue byte count or the queue is empty. Bandwidth used by a particular queue can only be indirectly specified in terms of byte count and queue length.
Queue number 0 is a system queue; it is emptied before any of the queues numbered 1 through 10 are processed. The system enqueues high-priority packets, such as keepalive packets, to this queue. Other traffic cannot be configured to use this queue.
You can set up both priority queuing and custom queuing on your network, but you can assign only one or the other to an interface.
Following is a list of the priority-setting tasks that you can choose from, depending upon the needs of your network:
See the following sections for more information about these tasks.
You can establish queuing priorities based upon the protocol type. All Cisco-supported protocols are allowed. Perform one of the following tasks in global configuration mode:
Queue keywords provide additional options including byte-count, TCP services and port number assignments, and IP and Novell access list assignments.
You can assign a queue for those packets that did not match any other rule in the list. To do so, perform one of the following tasks in global configuration mode:
You can establish queuing priorities on packets entering from a specific interface. Perform the followint tasks in global configuration mode:
| Task | Command |
|---|---|
| Establish queuing priorities on packets entering from a given interface. | priority-list list interface interface-type interface-number {high | medium | normal | low} |
| Establish custom queuing based on packets entering from a given interface. | queue-list list interface interface-type interface-number queue-number |
You can specify the maximum number of packets that might be waiting in each of the priority queues. Perform the following tasks:
| Task | Command |
|---|---|
| Specify the maximum number of packets that can be waiting in each of the priority queues | priority-list list queue-limit high-limit medium-limit normal-limit low-limit |
| Specify the maximum number of packets that can be waiting in each of the priority queues | queue-list list queue queue-number limit limit-number |
| Designate the byte size allowed per queue. | queue-list list queue queue-number byte-count byte-count number |
Both the limit and byte-count keywords might appear as arguments to the queue-list list queue command.
You can assign a priority list number to an interface. Only one list can be assigned per interface. Perform the following tasks:
| Task | Command |
|---|---|
| Assign a priority list number to the interface. | priority-group list |
| Assign a custom queue list number to the interface. | custom-queue-list list |
On an interface, you can either apply priority queueing or custom queueng. With priority queuing, some lower priority queues might not get serviced at all, depending on the bandwidth used by packets in higher-priority queues. With the queue-list command, you can configure the amount of bandwidth used by a particular kind of traffic.
You can display information about the input and output queues when priority queuing is enabled on an interface.Perform either the of the following tasks in EXEC mode:
| Task | Command |
|---|---|
| Show the status of the priority queuing lists. | show queuing priority |
| Show the status of the custom queue lists. | show queuing custom |
If you enter the show queuing command without any keywords, status on both custom and priority queue lists are displayed.
You can adjust initial buffer pool settings and the limits at which temporary buffers are created and destroyed. To do so, perform one of the following tasks in global configuration mode:
During normal system operation, there are several pools of different sized buffers. These pools grow and shrink based upon demand. Some buffers are temporary and are created and destroyed as needed. Other buffers are permanently allocated and cannot be destroyed.
For examples of modifying the system buffer size, see the examples at the end of this chapter.
The server has one pool of queuing elements and five pools of packet buffers of different sizes. For each pool, the server keeps count 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.
To display statistics about the buffer pool on the system, perform the following task in EXEC mode:
| Task | Command |
| List statistics for the buffer pools. | show buffers [interface] |
Accounting management allows you to track both individual and group usage of network resources. You can then reallocate resources as needed. For example, you can change the system timers and configure TCP keepalives. See also the IP accounting feature, described in
the chapter"Configuring IP," in this manual.
Additional tasks for measuring system resources are covered in other protocol-specific chapters.
You can display stack utilization of processes and interrupt routines, including the reason for the last system reboot. This feature is useful for anaylzing system crashes. To display stack utilization, perform the following task in EXEC mode:
| Task | Command |
| Display stack utilization of processes and interrupt routines. | show stacks |
You can display memory pool statistics, including summary information about the activites of the system memory allocator and memory utilization. Perform the following tasks:
The following is a list of the examples in this section:
The following is an example of a typical system configuration file:
! Define line password
line 0 4
password secret
login
!
! Define privileged-level password
enable-password Secret Word
!
! Define a system hostname
hostname TIP
! Define host filenames
boot host host1-confg 131.108.1.111
boot host host2-confg 131.108.1.111
! Define system filenames
boot system sys1-system 131.108.13.111
boot system sys2-system 131.108.1.111
!
! Enable SNMP
snmp-server community
snmp-server trap-authentication
snmp-server host 131.108.1.27 public
snmp-server host 131.108.1.111 public
snmp-server host 131.108.2.63 public
!
! Define TACACS server hosts
tacacs-server host 131.108.1.27
tacacs-server host 131.108.13.33
tacacs-server host 131.108.1.33
!
! Define a message-of-the-day banner
banner motd ^C
The Information Place welcomes you
Please call 1-800-555-2222 for a login account, or enter
your password at the prompt.
^C
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 system will try to keep no more than 200 medium buffers free:
buffers middle max-free 200
In the following example, the system will try to create one large temporary extra buffer, just after a reload:
buffers large initial 1
In the following example, the system will try to create one permanent huge buffer:
buffers huge permanent 1
The following sample configuration sets up secret passwords on communication servers A, B, and C, thus enabling the three communication servers to connect to each other.
To authenticate connections between communication servers A and B, enter the following commands:
username B password a-b_secret
username A password a-b_secret
To authenticate connections between communication servers A and C, enter the following commands:
username C password a-c_secret
username A password a-c_secret
To authenticate connections between communication servers B and C, enter the following commands:
username C password b-c_secret
username B password b-c_secret
When you specify an encryption type of 0 to enter an unencrypted password, the system displays the encrypted version of the password. For example, suppose you enter the following command:
username bill password westward
The system would display this command like this:
username bill password 7 21398211
The encrypted version of the password is 21398211. The password was encrypted by the Cisco-defined encryption algorithm, as indicated by the "7."
If you were to enter the following command, the system would assume that the password is already encrypted and would do no encryption. It would display the command exactly as you typed it:
username bill password 7 21398211
username bill password 7 21398211
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