Configuring Dial Backup with Dialer Profiles

This chapter describes how to configure dialer interfaces, which can be configured as the logical intermediary between one or more physical interfaces and another physical interface that is to function as backup. It includes the following main sections:

To identify the hardware platform or software image information associated with a feature, use the Feature Navigator on Cisco.com to search for information about the feature or refer to the software release notes for a specific release. For more information, see the “Identifying Supported Platforms” section in the “Using Cisco IOS Software” chapter.

For a complete description of the dial backup commands in this chapter, refer to the Cisco IOS Dial Technologies Command Reference. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.

Dial Backup with Dialer Profiles Overview

A backup interface is an interface that stays idle until certain circumstances occur; then it is activated. Dialer interfaces can be configured to use a specific dialing pool; in turn, physical interfaces can be configured to belong to the same dialing pool.

See the section “Configuration Example of Dialer Profile for ISDN BRI Backing Up Two Leased Lines” at the end of this chapter for a comprehensive example of a dial backup interface using dialer profiles. In the example, one BRI functions as backup to two serial lines and can make calls to two different destinations.

How to Configure Dial Backup with Dialer Profiles

To configure a dialer interface and a specific physical interface to function as backup to other physical interfaces, perform the tasks in the following sections:

Configuring a Dialer Interface

To configure the dialer interface that will be used as an intermediary between a physical interface that will function as backup interface and the interfaces that will use the backup, use the following commands beginning in global configuration mode:

 

Command
Purpose

Step 1

Router(config)# interface dialer number

Creates a dialer interface and begins interface configuration mode.

Step 2

Router(config-if)# ip unnumbered loopback0

Specifies IP unnumbered loopback.

Step 3

Router(config-if)# encapsulation ppp

Specifies PPP encapsulation.

Step 4

Router(config-if)# dialer remote-name username

Specifies the Challenge Handshake Authentication Protocol (CHAP) authentication name of the remote router.

Step 5

Router(config-if)# dialer string dial-string

Specifies the remote destination to call.

Step 6

Router(config-if)# dialer pool number

Specifies the dialing pool to use for calls to this destination.

Step 7

Router(config-if)# dialer-group group - number

Assigns the dialer interface to a dialer group.

Configuring a Physical Interface to Function As Backup

To configure the physical interface that is to function as backup, use the following commands beginning in global configuration mode:

 

Command
Purpose

Step 1

Router(config)# interface type number

Specifies the interface and begins interface configuration mode.

Step 2

Router(config-if)# encapsulation ppp

Specifies PPP encapsulation.

Step 3

Router(config-if)# dialer pool-member number

Makes the interface a member of the dialing pool that the dialer interface will use; make sure the number arguments have the same value.

Step 4

Router(config-if)# ppp authentication chap

Specifies CHAP authentication.

Configuring Interfaces to Use a Backup Interface

To configure one or more interfaces to use a backup interface, use the following commands beginning in global configuration mode:

 

Command
Purpose

Step 1

Router(config)# interface type number

Specifies the interface to be backed up and begins interface configuration mode.

Step 2

Router(config-if)# ip unnumbered loopback0

Specifies IP unnumbered loopback.

Step 3

Router(config-if)# backup interface dialer number

Specifies the backup interface and begins interface configuration mode.

Step 4

Router(config-if)# backup delay enable-delay disable-delay

Specifies delay between the physical interface going down and the backup being enabled, and between the physical interface coming back up and the backup being disabled.

Configuration Example of Dialer Profile for ISDN BRI Backing Up Two Leased Lines

The following example shows the configuration of a site that backs up two leased lines using one BRI. Two dialer interfaces are defined. Each serial (leased line) interface is configured to use one of the dialer interfaces as a backup. Both of the dialer interfaces use dialer pool 1, which has physical interface BRI 0 as a member. Thus, physical interface BRI 0 can back up two different serial interfaces and can make calls to two different sites.

interface dialer0
ip unnumbered loopback0
encapsulation ppp
dialer remote-name Remote0
dialer pool 1
dialer string 5551212
dialer-group 1
 
interface dialer1
ip unnumbered loopback0
encapsulation ppp
dialer remote-name Remote1
dialer pool 1
dialer string 5551234
dialer-group 1
 
interface bri 0
encapsulation PPP
dialer pool-member 1
ppp authentication chap
 
interface serial 0
ip unnumbered loopback0
backup interface dialer 0
backup delay 5 10
 
interface serial 1
ip unnumbered loopback0
backup interface dialer1
backup delay 5 10