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This chapter lists dial backup and DDR commands, explains command syntax, and provides usage guidelines.
Dial backup provides protection against WAN downtime by allowing you to configure a backup serial line circuit-switched connection
Dial-on demand routing (DDR) provides network connections across the Public Switched Telephone Network (PSTN). Traditionally, networks have been interconnected using dedicated lines for WAN connections. With DDR, you can use modems to establish low-volume, periodic network connections over public circuit-switched networks.
For information about configuring DDR and configuration examples, refer to the Communication Server Configuration Guide.
Use the backup delay interface configuration command to define how much time should elapse before a secondary line status changes after a primary line status has changed. Use the no backup delay command to return to the default, which means as soon as the primary fails, the secondary is immediately brought up without delay.
backup delay {enable-delay | never} {disable-delay | never}| enable-delay | Number of seconds that elapse after the primary line goes down before the communication server activates the secondary line. |
| disable-delay | Number of seconds that elapse after the primary line goes up before the communication server deactivates the secondary line. |
| never | Prevents the secondary line from being activated or deactivated. |
0 seconds
Interface configuration
For environments in which there are spurious signal disruptions that might appear as intermittent lost carrier signals, it is recommended that some delay be enabled before activating and deactivating a secondary line.
The following example sets a 10-second delay on deactivating the secondary line (interface serial 0) however, the line is activated immediately.
interface serial 0
backup delay 0 10
Use the backup interface interface configuration command to configure the serial interface as a secondary or dial backup line. Use the no backup interface command with the appropriate serial port designation to turn this feature off.
backup interface interface number| interface | The type of interface. This is always serial. |
| number | Serial port to be set as the secondary line. |
None
Interface configuration
The interface you define with this command can only back up one interface.
The following example sets serial 1 as the backup line:
interface async 0
backup interface serial 1
Use the backup load interface configuration command to set traffic load threshold for dial backup service. Use the no backup command to remove this setting.
backup load {enable-threshold | never} {disable-load | never}| enable-threshold | Percentage of the primary line's available bandwidth. |
| disable-load | Percentage of the primary line's available bandwidth. |
| never | Sets the secondary line to never be activated sue to traffic load. |
None
Interface configuration
When the transmitted or received load on the primary line is greater than the value assigned to the enable-threshold argument, the secondary line is enabled.
The secondary line is disabled when one of the following conditions occur:
If the never keyword is used instead of an enable-threshold value, the secondary line is never activated because of a traffic load. If the never keyword is used instead of a disable load argument, the secondary line is never activated because of traffic load.
The following example sets the traffic load threshold to 60 percent of the primary line serial 0. When that load is exceeded, the secondary line is activated, and will not be deactivated until the combined load is less than 5 percent of the primary bandwidth.
interface serial 0
backup load 60 5
Use the chat-script global configuration command to create a script that will place a call over a modem. Use the no form of the command to disable the specified chat script.
chat-script script-name expect send...| script-name | Name of the chat script. |
| expect send... | Content of the chat script. |
No chat scripts are configured by default.
Global configuration
Chat scripts are used in dial-on-demand routing to give commands to dial a modem and commands to log onto remote systems. The defined script will be used to place a call over a modem.
Some characteristics of chat scripts are as follows:
A string within " " characters is treated as a single entity.
It is recommended that one chat script (a "modem" chat script) be written for placing a call and another chat script (a "system" or "login" chat script) be written to log onto remote systems, where required.
A suggested chat script naming convention is as follows:
vendor-type-modulationIn other words, the syntax of the chat-script command becomes the following:
chat-script vendor-type-modulation expect send...For example, if you have a Telebit t3000 modem that uses V.32bis modulation, you would name your chat script as follows:
telebit-t3000-v32bis
For example, the chat-script command could become the following:
CS# chat-script telebit-t3000-v32bis ABORT ERROR ABORT BUSY ABORT "NO ANSWER" "" "AT H" OK "AT DT \T" DIALING \c TIMEOUT 30 CONNECT \c
For example, you could have script names like the following:
Adhering to this naming convention allows you to use partial chat script names with regular expressions to specify a range of chat scripts that can be used. This is particularly useful for dialer rotary groups and is explained further in the next section.
Chat scripts are in the form expect send..., where the send string following the hyphen is executed if the preceding expect string fails. Each send string is followed by a return unless it ends with \c. ^x gets translated into the appropriate control character, and \x gets translated into x if \x is not one of the special sequences listed in Table 1-1.
See the book entitled Managing uucp and Usenet by Tim O'Reilly and Grace Todino for more information about chat scripts.
The escape sequences used in chat scripts are listed in the following table.
| Escape Sequence | Description |
|---|---|
" "
| Expect a null string. |
| EOT | Send an end-of-transmission character. |
| BREAK | Cause a BREAK. This is sometimes simulated using line speed changes and null characters. May not work on all systems. |
| \c | Suppress newline at the end of the send string. |
| \d | Delay for two seconds. |
| \K | Insert a BREAK. |
| \n | Send a newline or linefeed character. |
| \p | Pause for 1/4 second |
| \r | Send a return. |
| \s | Send a space character. |
| \t | Send a table character |
| \\ | Send a backslash (\) character. |
| \T | Replaced by phone number. |
| \q | Reserved, not yet used |
Sample supported expect-send pairs are described in Table 1-2.
| Expect and Send Pair | Function |
|---|---|
| ABORT string | Starts scanning for the string in the input and if it is seen this indicates that the chat script has failed. |
| TIMEOUT time | Sets the time to wait for input, in seconds. The default is five seconds. |
As an example of how expect-send pairs function, if the modem reports BUSY when the number is busy, you can indicate that you want the attempt stopped at his point by including ABORT BUSY in your chat script.
ABORT sink instead of ABORT ERROR means that the system will abort when it sees sink instead of when it sees ERROR.
After the connection is established and return is entered, a second RETURN is often required before the prompt appears.
You might include the following as part of your chat script:
ssword:-/r-sswrod
This means that after the connection is established, you want "ssword" to be displayed. If it is not displayed, after the timeout period send a RETURN again.
The following example shows the chat-script command being used to create a chat script named t3000:
CS# chat-script t3000 ABORT ERROR ABORT BUSY ABORT "NO ANSWER" "" "AT H" OK "AT DT \T" DIALING \c TIMEOUT 30 CONNECT \c
Use the dialer enable-timeout interface configuration command to set the length of time an interface stays down after a call has completed or failed, before it is available to dial again. Use the no dialer enable-timeout command to reset the enable timeout value to the default.
dialer enable-timeout number-of-seconds| number-of-seconds | Number of seconds that the communication server waits before the next call can occur on the specific interface. Acceptable values are positive, nonzero integers. |
15 seconds
Interface configuration
This command applies to inbound and outbound calls.
If your phone lines are busy or down, you might want to enforce a certain period of time before the system repeats an attempt to make a connection with a remote site. Configuring this timeout can prevent outgoing lines and switching equipment from being needlessly loaded down.
The following example specifies a waiting period of 30 seconds on interface async 1:
interface async 1
dialer enable-timeout 30
Use the dialer fast-idle interface configuration command to specify the amount of time that a line for which there is contention will stay idle before the line is disconnected and the competing call is placed. Use the no dialer fast-idle command to reset the timeout period to the default.
dialer fast-idle number-of-seconds| number-of-seconds | Idle time, in seconds, that must occur on an interface before the line is disconnected. Acceptable values are positive, nonzero integers. |
20 seconds
Interface configuration
The fast idle timer is activated if there is contention for a line. In other words, if a line is busy, a packet for a different next hop address is received, and the busy line is required to send the competing packet, the dialer fast idle timer is activated.
If the line becomes idle for configured length of time, the current call is disconnected immediately and the new call is placed.
If the line has not yet been idle as long as the fast idle timer, the packet is dropped because there is no way to get through to the destination. After the packet is dropped, the fast idle timer remains active and the current call is disconnected as soon as it has been idle for as long as the fast idle timeout.
If, in the meanwhile, there is another packet transmitted to the currently connected destination, and it is classified as interesting, the fast idle timer will be restarted.
This command applies to inbound and outbound calls.
Combining this command with the dialer idle-timeout command allows you to configure lines to stay up for a longer period of time when there is not contention, but to be reused more quickly when there not enough lines for the current demand.
The following example specifies a fast idle timeout of 35 seconds on interface async 1:
interface async 1
dialer fast-idle 35
dialer idle-timeout
dialer map
Use the dialer-group interface configuration command to control access. You must specify the number of a dialer access group to which a specific interface is assigned. Use the no dialer-group command to remove an interface from the specified dialer access group.
dialer-group group-number| group-number | Number of the dialer access group to which the specific interface belongs. This access group is defined using the dialer-list command. Acceptable values are nonzero, positive integers between 1 and 10. |
None
Interface configuration
An interface can only be associated with a single dialer access group; multiple dialer-group assignment is not allowed. A second dialer access group assignment will override the first. A dialer access group is defined with the dialer-group command. The dialer-list command associates an access list with a dialer access group.
The following example specifies dialer access group number 1.
If there is a dialer-list command associated with the dialer group 1, the destination address of the packet is evaluated against the access list specified in the associated dialer-list command. If it passes, a call is initiated (if no connection has already been established) or the idle timer is reset (if a call is currently connected).
interface async 1
dialer-group 1
dialer-list
Use the dialer idle-timeout interface configuration command to specify the idle time before the line is disconnected. Use the no dialer idle-timeout command to reset the idle timeout to the default.
dialer idle-timeout number-of-seconds| number-of-seconds | Idle time, in seconds, that must occur on an interface before the line is disconnected. Acceptable values are positive, nonzero integers. |
120 seconds
Interface configuration
This command is used on lines for which there is no contention. When contention occurs, the dialer fast-idle command is activated. For example, when a busy line is requested to send another packet to a different destination than it is currently connected to, line contention occurs and the dialer fast-idle command is activated.
This command applies to inbound and outbound calls. For example, if a receiving system needs to make outgoing calls, you might configure it with a short idle timeout.
The following example specifies of an idle timeout of 3 minutes (180 seconds) on interface async 1:
interface async 1
dialer idle-timeout 180
dialer fast-idle
Use the dialer in-band interface configuration command to specify that DDR is to be supported. The dialer in-band command specifies that chat scripts will be used on asynchronous interfaces and V.25bis will be used on synchronous interfaces. Use the no dialer in-band command to disable dial-on-demand routing for the interface.
dialer in-band [no-parity | odd-parity]| no-parity | No parity is applied to the dialer string that is sent out to the modem on synchronous interfaces. |
| odd-parity | Dialed number will have odd parity (7-bit ASCII characters with the eighth bit the parity bit) on synchronous interfaces. |
Disabled. By default, no parity is applied to the dialer string.
Interface configuration
The parity keywords do not apply to asynchronous interfaces.
The parity setting applies to the dialer string that is sent out to the modem. If you do not specify a parity, or if you specify no parity, no parity is applied to the output number. If odd parity is configured, the dialed number will have odd parity (7-bit ASCII characters with the eighth bit the parity bit.)
If an interface is only accepts calls and does not place calls, the dialer in-band interface configuration command is the only command needed to configure it. If an interface is configured in this manner, with no dialer rotary groups, the idle timer never disconnects the line. It is up to the remote end (the end that placed the call) to disconnect the line based on idle time.
The following example specifies DDR for async 1:
interface async 1
dialer in-band
dialer map
dialer string
Use the dialer-list list global configuration command to group access lists. This command applies access lists to dialer access groups to control automatic dialing using DDR with standard IP access lists. Use the no dialer-list list global configuration command to disable automatic dialing.
dialer-list dialer-group list list-number| dialer-group | Specifies the number of a dialer access group identified in any dialer-group interface configuration command. |
| list-number | Specifies the access list number specified in any IP or Novell IPX access lists including Novell IPX extended, Service Access Point (SAP) access lists and bridging type. See Table 1-3 for the supported access list types and numbers. |
| Access List Type | Access List Number Range |
|---|---|
| Standard IP | 1-99 |
| Extended IP | 100-199 |
| Standard Novell IPX | 800-899 |
| Extended Novell IPX | 900-999 |
None
Global configuration
This command applies access lists to dialer access groups defined with the dialer-group command. See the Communication Server Configuration Guide for more information about configuring IP access lists.
In the following example, dialing occurs when an interesting packet (one that matches access list specifications) needs to be output on an interface. Using the standard access list method, packets can be classified as interesting or uninteresting. To specify that IGRP TCP/IP routing protocol updates are not interesting (relative to DDR automatic dialing), the following access list would be defined:
access-list 101 deny igrp 0.0.0.0 255.255.255.255 255.255.255.255 0.0.0.0
To permit all other IP traffic, the preceding would be modified as follows:
access-list 101 permit ip 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255
Then the following command would be used to place list 101 into dialer access group 1:
dialer-list 1 list 101
dialer-group
Use the dialer-list protocol global configuration command to control automatic dialing by a protocol name. Use the no dialer-list commands to disable automatic dialing.
dialer-list dialer-group protocol protocol-name {permit | deny}| dialer-group
| Number of a dialer access group identified in any dialer-group interface configuration command. |
| protocol-name | One of the supported protocols as listed in Table 1-4. |
| Keyword | Protocol |
|---|---|
| ip | IP |
| ipx | Novell IPX |
None
Global configuration
Using the dialer-list protocol command provides a coarse method of access control by permitting or denying an entire protocol. For more refined access control, use the dialer-list list command to specify an access list.
dialer-group
dialer-list list
To configure bandwidth on demand by setting the maximum load before the dialer places another call to a destination, use the dialer load-threshold interface subcommand. To disable the setting, use the no version of the command.
dialer load-threshold load| load | Specifies the interface load beyond which the dialer will initiate another call to the destination. This argument is a number between 1 and 255. |
Disabled
Interface configuration
This command applies to dialer rotary groups only.
If a packet is transmitted on a dialer interface, there is a call established, and the transmit load on the interface exceeds the specified load threshold, the dialer will initiate another call to the destination. The dialer will make additional calls as necessary to expand bandwidth but will never interrupt an existing call to another destination.
The argument load is the calculated weighted average load value for the interface; 1 is unloaded, 255 is fully loaded. The load is calculated by the system dynamically, based on bandwidth. You must set the bandwidth for an interface in kilobits per second, using the bandwidth command.
The load calculation determines how much of the total bandwidth you are using, where 255 means that you are using one hundred percent of the bandwidth.
See the interface configuration chapter for a full description of the bandwidth command.
In the following example, if the load to a particular destination on an interface in dialer rotary group 5 exceeds interface load 200, the dialer will initiate another call to the destination.
interface dialer 5
dialer load-threshold 200
bandwidth (+)
interface dialer
dialer rotary-group
Use the dialer map interface configuration command to configure a multiple dialing destinations on a single synchronous interface.
dialer map protocol next-hop-address dial-string| protocol | Name of the protocol. |
| next-hop-address | Protocol address used to match against addresses to which packets are destined. |
| dial-string | Telephone number sent to the dialing device when it sees packets with the specified next-hop-address that matches the access lists defined. |
None
Interface configuration
Use this command to configure multiple dialing destinations for single lines, multiple lines, or a dialer rotary group. This command is for synchronous serial interfaces. Use the dialer map modem-script system-script command to configure multiple dialing destinations on asynchronous interfaces.
In the following example, interface serial 0 is configured for DDR and two dialing destinations:
interface serial 1
dialer in-band
dialer map ip 1.1.1.1 5555555
dialer map ip 2.2.2.2 6666666
ppp authentication chap
username
dialer map
dialer map modem-script system-script
dialer map modem-script system-script name
Use the dialer map modem-script system-script interface configuration command to place a call to any of the following:
Use the no form of the command to delete the mapping.
dialer map protocol next-hop-address [modem-script modem-regexp] [system-script| protocol | Name of the protocol. |
| next-hop-address | Protocol address used to match against addresses to which packets are destined. |
| modem-script | (Optional.) Modem script to be used for the connection (for asynchronous interfaces). |
| modem-regexp | (Optional.) Regular expression to which a modem script will be matched (for asynchronous interfaces). |
| system-script | (Optional.) System script to be used for the connection (for asynchronous interfaces). |
| system-regexp | (Optional.) Regular expression to which a system script will be matched for asynchronous interfaces). |
| dial-string | Telephone number sent to the dialing device when it sees packets with the specified next-hop-address that matches the access lists defined. |
None
Interface configuration
Specify chat scripts for a physical interface that is not part of a dialer rotary group if:
Configure a dialer map command for each remote destination for the specified interface.
You do not need to specify a system script if:
If you adhered to the chat script naming convention described earlier in this chapter, use the form [modem-script *modulation-type] in the dialer map command, as in as in ".*-v32bis." This allows you to specify the modulation type that is best for the system you are calling, and allows the modem type for the line to be specified by the modem chat-script command.
The expression "." is a wildcard that matches any character, and the expression "*" indicates that the preceding character can be duplicated multiple times. For more information about regular expressions, see Appendix B, "Regular Expressions," in this manual.
If there is a modem script specified in the dialer map interface configuration command and a modem script specified in the modem chat-script line configuration command, the first chat script that matches both will be used. If no script matches both, an error message is logged and the connection is not established. If there is no modem chat script specified for the line, the first chat script (that is, the one specified using the chat-script global configuration command) that matches the modem script regular expression will be used. If there is a system script specified in the dialer map interface configuration command, the first chat script to match the regular expression will be used.
The modem-script and system-script keywords and corresponding arguments are optional. They are ignored on synchronous interfaces.
If you have named your chat script according to the type of modem and modulation (for example, codex-v32 or telebit v32), your regular expression could be codex-.* in the modem chat-script line configuration command, and *-v32bis in the modem script specified in the dialer map command for a system that you wish to connect to using v32bis modulation.
The modem lines (specified by the argument regexp in the modem chat-script line configuration command) would be set to one of the following regular expressions to match patterns, depending on what kind of modem you have:
The following example shows a dialing chat script and a login chat script. The
dialer in-band command enables DDR on asynchronous interface 10 and the dialer map command looks for the specified dialing and the login scripts, and then uses those scripts to dial 96837890.
chat-script dial ABORT ERROR "" "AT Z" OK "ATDT \T" TIMEOUT 30 CONNECT \c
chat-script login ABORT invalid TIMEOUT 15 name: billw word: wewpass ">"
"slip default"
interface async 10
dialer in-band
dialer map ip 10.55.0.1 modem-script dial system-script login 96837890
chat-script
modem chat-script
Use the dialer map modem-script system-script name interface configuration command to configure a serial interface to call multiple sites and to authenticate calls from multiple sites. Use the no form of the command to delete a particilar dialer map entry.
dialer map protocol next-hop-address [modem-script modem-regexp] [system-script| protocol | Name of the protocol. |
| next-hop-address | Protocol address used to match against addresses to which packets are destined. |
| modem-script | (Optional.) Modem script to be used for the connection (for asynchronous interfaces). |
| modem-regexp | (Optional.) Regular expression to which a modem script will be matched (for asynchronous interfaces). |
| system-script | (Optional.) System script to be used for the connection (for asynchronous interfaces). |
| system-regexp | (Optional.) Regular expression to which a system script will be matched for asynchronous interfaces). |
| name | Remote system with which the local communication server communicates. |
| hostname | Name of the remote device (usually the host name). |
| dial-string | Telephone number sent to the dialing device when it sees packets with the specified next-hop-address that matches the access lists defined. |
None
Interface configuration
With an interface configured for CHAP and the name hostname keyword argument pair, the local device will authenticate the remote site using CHAP, which will transmit the remote site's host name to the central site. The central site will then use this name to authenticate the caller, and will use the next hop address to transmit packets to the remote site. Because no dialer string is specified, the central site cannot call the remote communciation server.
Specify chat scripts for a physical interface that is not part of a dialer rotary group if no chat script is specified for the line and/or an additional (system) chat script is required to log onto the remote system.
Configure a dialer map command for each remote destination for the specified interface.
You do not need to specify a system script if: either of the following is true:
If you adhered to the chat script naming convention described earlier in this chapter, use the form [modem-script *modulation-type] in the dialer map command, as in as in ".*-v32bis." This allows you to specify the modulation type that is best for the system you are calling, and allows the modem type for the line to be specified by the modem chat-script command.
The expression "." is a wildcard that matches any character, and the expression "*" indicates that the preceding character can be duplicated multiple times. For more information about regular expressions, see Appendix B, "Regular Expressions," in this manual.
If there is a modem script specified in the dialer map interface configuration command and a modem script specified in the modem chat-script line configuration command, the first chat script that matches both will be used. If no script matches both, an error message is logged and the connection is not established. If there is no modem chat script specified for the line, the first chat script (that is, the one specified using the chat-script global configuration command) that matches the modem script regular expression will be used. If there is a system script specified in the dialer map interface configuration command, the first chat script to match the regular expression will be used.
The modem-script and system-script keywords and corresponding arguments are optional. They are ignored on synchronous interfaces.
If you have named your chat script according to the type of modem and modulation (for example, codex-v32 or telebit v32), your regular expression could be codex-.* in the modem chat-script line configuration command, and *-v32bis in the modem script specified in the dialer map command for a system that you wish to connect to using v32bis modulation.
The modem lines (specified by the argument regexp in the modem chat-script line configuration command) would be set to one of the following regular expressions to match patterns, depending on what kind of modem you have:
The following example shows a dialing chat script and a login chat script. The
dialer in-band command enables DDR on asynchronous interface 10 and the dialer map command looks for the specified dialing and the login scripts, and then uses those scripts to dial 96837890.
chat-script dial ABORT ERROR "" "AT Z" OK "ATDT \T" TIMEOUT 30 CONNECT \c
chat-script login ABORT invalid TIMEOUT 15 name: billw word: wewpass ">"
"slip default"
interface async 10
dialer in-band
dialer map ip 10.55.0.1 modem-script dial system-script login 96837890
chat-script
modem chat-script
Use the dialer map name interface configuration command to configure a dialer rotary group to receive and take advantage of caller identification using CHAP. The no dialer map name command deletes a particular dialer map entry.
dialer map protocol next-hop-address name hostname| protocol | Name of the protocol. |
| next-hop-address | Protocol address used to match against addresses to which packets are destined. |
| name | Remote system with which the local communication server communicates. |
| hostname | Name of the remote device (usually the host name). |
None
Interface configuration
This form of the dialer map command is used in configurations in which remote sites are calling a central site, but the central site is not calling the remote site. With this command, the local device will authenticate the remote site using CHAP, which will transmit the remote site's host name to the central site. The central site will then use this name to authenticate the caller, and will use the next hop address to transmit packets to the remote site. Because there is no dialer string specified, the central site cannot call the remote communication server.
In the following example, a remote site is calling a central site, but the central site is not calling the remote site. The local device will authenticate the site that is calling in using CHAP. CHAP will cause the remote site's name, YYY, to be transmitted to the site it is calling. The central site will then use this name to authenticate the remote site.
interface async 1
encapsulation ppp
ppp authentication chap
dialer map ip 131.108.2.5 name YYY
ppp authentication chap
username
dialer map
dialer map modem-script system-script
dialer map modem-script system-script name
To set the priority of an interface in a dialer rotary group use the dialer priority interface configuration command. Use the no form of the command to revert to the default setting.
dialer priority n| n | Specifies the priority of an interface in a dialer rotary group; the lowest number indicates the highest priority. A number from 0 to 255. . |
0
Interface configuration
The value 0 indicates the lowest priority and 255 indicates the highest priority. The dialer priority command controls which interfaces within a dialer rotary group will be used first. Higher priority interfaces (configured with higher n value) are used first. This command is only meaningful for interfaces that are part of dialer rotary groups.
The priority command gives the administrator the ability to tell the dialer rotary group which free interface (and by extension which modem) to use first. This command applies to outgoing calls only.
In the following example, interface async 3 will be used after interfaces with higher and before interfaces with lower priority.
interface async 3
dialer priority 5
For example, a 500-CS has a selection of 14400 modems on it. Some of them are perceived to be better performers than others. You also have two 4800-bps, three 1200-bps, and one 300-bps modem. They are all on interfaces that are in a dialer rotary group. You do not want the 500-CS to make the call on the 300-baud modem if any of the faster modems are free. You want the 500-CS to use the highest-performance modems first, and the slowest modems last.
interface dialer
dialer rotary-group
Use the dialer rotary-group interface configuration command to include an interface in a dialer rotary group.
dialer rotary-group number| number | Number of the dialer interface in whose rotary group you want this interface included. An integer that you select that indicates the dialer rotary group; defined by the interface dialer command. A number from 0 to 255. |
None
Interface configuration
The following example places async interfaces 1 and 2 into dialer rotary group 1, defined by the interface dialer 1 command:
hostname central-site
! PPP encapsulation is enabled for interface dialer 1.
interface dialer 1
encapsulation ppp
dialer in-band
ip address 131.108.2.1 255.255.255.0
ip address 131.126.4.1 255.255.255.0 secondary
! The first dialer map command allows the central site and remote site YYY
! and to call each other and allows the central site to authenticate site YYY
! when it calls in. The second dialer map command, with no! dialer string,
! allows the central site to authenticate remote site ZZZ when it calls in, but
! the central site cannot call remote site ZZZ (no phone number).
dialer map ip 131.108.2.5 name YYY 14155553434
dialer map ip 131.126.4.5 name ZZZ
! The DTR pulse signals for three seconds on the interfaces in dialer
! group 1. This holds the DTR low so the modem can recognize that DTR has been
! dropped.
pulse-time 3
! Interfaces async 1 and async 2 are placed in dialer rotary group 1.
! All of the interface configuration commands (the encapsulation and dialer
! map commands shown earlier in this example) applied to interface
! dialer 1 apply to the physical interfaces assigned to the dialer group.
interface async 1
dialer rotary-group 1
interface async 2
dialer rotary-group 1
interface dialer
Use the dialer string interface configuration command to specify the string (telephone number) to be called for interfaces calling a single site. Use the no dialer string command to delete the dialer string specified for the interface.
dialer string dial-string| dial-string | String of characters to be sent to a DCE. |
None
Interface configuration
To use this command on an asynchronous interface, a modem chat script must be defined for the associated line, by using the modem chat-script command. A script must be used to implement dialing.
Dialers configured as in-band pass the string to the external dialing device. Specify one dialer string command per interface.
To specify multiple strings, use the dialer map command. In general, you include a dialer string or dialer map command if you intend to use a specific interface to initiate a DDR call.
The string of characters specified for the dial-string argument is the default number used under the following conditions:
On synchronous interfaces, depending on the type of modem you are using, CCITT V.25bis options might be supported as dial-string parameters of the dialer string command. Supported options are listed in Table 1-5. The functions of the parameters are nation specific, and they may have different implementations in your country. These options apply only if you have enabled DDR with the dialer in-band command. Refer to the operation manual for your modem for a list of supported options.
| Option | Description |
|---|---|
| : | Wait tone. |
| < | Pause.
Usage and duration of this parameter vary by country. |
| = | Separator 3.
For national use. |
| > | Separator 4
For national use. |
| P | Dialing to be continued in pulse mode.
Optionally accepted parameter. |
| T | Tone (Dialing to be continued in Dual Tone Multifrequency, DTMF, mode).
Optionally accepted parameter. |
| & | Flash. (The flash duration varies by country.)
Optionally accepted parameter. |
The following example specifies a DDR telephone number to be tone dialed on interface async 1 using the dialer string command:
interface async 1
dialer string T14085553434
dialer-group
dialer in-band
dialer map
modem chat-script
Use the dialer wait-for-carrier-time interface configuration command to specify how long to wait for a carrier. On asynchronous interfaces, this command sets the total time allowed for the chat script to run. Use the no dialer wait-for-carrier-time command to reset the carrier wait time value to the default.
dialer wait-for-carrier-time number-of-seconds| number-of-seconds | Number of seconds that the interface waits for the carrier to come up when a call is placed. Acceptable values are positive, nonzero integers. |
30 seconds
Interface configuration
If a carrier signal is not detected in this amount of time, the interface is disabled until the enable timeout occurs (configured with the dialer enable-timeout command).
The following example specifies a carrier wait time of 45 seconds on interface async 1:
interface async 1
dialer wait-for-carrier-time 45
dialer enable-timeout
Use the encapsulation ppp interface configuration command to configure Point-to-Point Protocol (PPP) encapsulation.
encapsulation pppThis command has no arguments or keywords.
Disabled
Interface configuration
The Point-to-Point Protocol (PPP), described in RFCs 1331 and 1332, is designed to encapsulate Internet Protocol (IP) and IPX datagrams and other network layer protocol information over point-to-point links.
The current implementation of PPP supports no configuration options. The software sends no options, and any proposed options are rejected.
Of the possible upper-layer protocols, only IP is supported at this time. Thus, the only upper-level protocol that can be sent or received over a point-to-point link using PPP encapsulation is IP. Refer to RFC 1134 for definitions of the codes and protocol states.
PPP echo requests also can be used as keepalives, to minimize disruptions to the end users of your network. The no keepalive command can be used to disable echo requests.
The following example enables PPP encapsulation on interface async 1.
interface async 1
encapsulation ppp
A dagger (+) indicates that the command is documented in another chapter.
keepalive+
ppp authentication chap
Use the interface dialer global configuration command to define a dialer rotary group.
interface dialer number| number | Number of the dialer rotary group. It can be number in the range 0 through 255. |
None
Global configuration
Dialer rotary groups allow you to apply a single interface configuration to a set of physical interfaces. This allows a group of interfaces to be used as a pool of interfaces for calling many destinations.
Once the interface configuration is propagated to a set of interfaces, those interfaces can be used to place calls using the standard DDR criteria. When multiple destinations are configured, any of these interfaces can be used for outgoing calls.
Dialer rotary groups are useful in environments that require multiple calling destinations. Only the rotary group needs to be configured with all of the dialer map commands. The only configuration required for the interfaces is the dialer rotary-group command indicating that each interface is part of a dialer rotary group.
Although a dialer rotary group is configured as an interface, it is not a physical interface. Instead it represents a group of interfaces. Interface configuration commands entered after the interface dialer command will be applied to all physical interfaces assigned to specified rotary groups. Individual interfaces in a dialer rotary group do not have individual addresses. The dialer interface has an address, and that address is used by all interfaces in the dialer rotary group.
The following example identifies interface dialer 1 as the dialer rotary group leader. Interface dialer 1 is not a physical interface, but represents a group of interfaces. The interface configuration commands that follow apply to all interfaces included in this group.
interface dialer 1
encapsulation ppp
authentication chap
dialer in-band
ip address 1.2.3.4
dialer map ip 1.2.2.5 name YYY 1415553434
dialer map ip 1.3.2.6 name ZZZ
Use the modem chat-script line configuration command for asynchronous lines to set a regular expression for a script on a modem line.
modem chat-script regexp| regexp | Regular expression to be used to select a chat script. The chat script name will be matched to regexp. |
None
Line configuration
Scripts are used to give commands to dial modems and commands to log onto remote systems. The regular expression is used to specify the name of the modem script that is to be executed. The first script that matches the argument regexp in this command and the dialer map command will be used. For more information about regular expressions, see Appendix B, "Regular Expressions."
If you adhered to the recommended naming convention for chat scripts, the modem lines (the argument regexp in the modem chat-script command) would be set to one of the following regular expressions to match patterns, depending on what kind of modem you have:
In the dialer map command, you could specify the modulation but leave the type of modem unspecified, as in ".*-v32bis."
The following example shows line chat scripts being specified for lines connected to Telebit and US Robotics modems:
! Some lines have telebit modems
line 1 6
modem chat-script telebit.*
! Some lines have US robotics modems
line 7 12
modem chat-script usr.*
chat-script
dialer map modem-script system-script
dialer map modem-scritp system-script name
system-script
Use the ppp authentication chap interface configuration command to enable Challenge Handshake Authentication Protocol (CHAP) on a serial interface. Use the no ppp authentication chap command to disable this encapsulation.
ppp authentication chapThis command has no arguments or keywords.
Disabled
Interface configuration
Once you have enabled CHAP, the local communication server requires authentication from remote devices. If the remote device does not support CHAP, no traffic will be passed to that device.
The following example enables the CHAP on interface serial 4:
interface async 4
ppp authentication chap
A dagger (+) indicates that the command is documented in another chapter.
encapsulation ppp+
Use the show dialer EXEC command to obtain a general diagnostic display for serial interfaces configured for DDR.
show dialer [interface interface type]| interface | (Optional.) Information for the interface specified by the arguments interface and unit is to be displayed. |
| interface unit | (Optional.) Interface and unit identifiers. |
EXEC
The following is a sample output from the show dialer command:
speedy# show dialer int async 1
Async1 - dialer type = IN-BAND NO-PARITY
Idle timer (900 secs), Fast idle timer (20 secs)
Wait for carrier (30 secs), Re-enable (15 secs)
Time until disconnect 838 secs
Current call connected 0:02:16
Connected to 8986
Dial String Successes Failures Last called Last status
8986 0 0 never Default
8986 8 3 0:02:16 Successful
speedy#
Table 1-6 describes significant fields shown in the display.
| Field | Description |
|---|---|
| Async 1 | Name of an asynchronous interface. |
| dialer type = IN-BAND | Indicates that DDR is enabled. |
| Idle timer (900 secs) | Idle timeout specification (in seconds). |
| Fast idle timer (20 secs) | Fast idle timer specification (in seconds). |
| Wait for carrier (30 secs) | Wait for carrier timer specification (in seconds). |
| Re-enable (15 secs) | Enable timeout specification (in seconds). |
| Dial string | Dial strings (telephone numbers) of logged calls. |
| Time until disconnect | Time until line is configured to disconnect. |
| Current call connected | Time at which the current call was connected. |
| Connected to | Dial string to which line is currently connected. |
| Successes | Successful connections (even if no data is passed). |
| Failures | Failed connections; call not successfully completed. |
| Last called | Time that last call occurred to specific dial string. |
| Last status | Status of last call to specific dial string (successful or failed). |
| Default | If the DDR facility is using the dial string specified with the dialer string command, the word Default is appended to the Last status entry. |
If an interface is connected to a destination, a display is provided that indicates the idle time before the line is disconnected (decrements each second). Then the duration of the current connection is shown. The following shows an example of this display; it would appear after the third line in the show dialer display.
Time until disconnect 596 secs
Current call connected 0:00:25
After a call disconnects, the system displays the time remaining before being available to dial again. The following is an example of this display; it would appear after the third line in the show dialer display:
Time until interface enabled 8 secs
If the show dialer interface command is issued for an interface on which DDR is not enabled, the system displays an error message. The following is an example error message:
Async 1 - Dialing not enabled on this interface.
If an interface is configured for DDR, the show interfaces command now displays the following message:
Async1 is up, line protocol is up (spoofing)
Hardware is Async Serial
The spoofing indicates that the line really is not up, but the dialer is forcing the line to masquerade as "up" so that upper level protocols will continue to operate as expected.
Use the username global configuration command to specify the password to be used in CHAP caller identification.
username name password secret| name | Host name, server name, user ID, or command name. |
| password | Possibly an encrypted password for this username. |
| secret | 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 eleven 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. |
None
Global configuration
Add a name entry for each remote system that the local communication server requires authentication from.
The username command is 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, you add a username entry.
If there is no secret specified and debug serial-interface is enabled, an error is displayed when a link is established and the CHAP challenge is not implemented. Debugging information on CHAP is available using the debug serial-interface and debug serial-packet commands. See the Debug Command Reference.
The following example configuration enables CHAP on interface serial 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 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 Eve password 7 121F0A18
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