Using Dialer Interfaces for Backup

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R4(config)# interface bri 0/0 R4(config-if)# no ip address R4(config-if)# encapsulation ppp R4(config-if)# dialer pool-member 1

R4(config-if)# exit

R4(config)# dialer-list 1 protocol ip permit R4(config)# interface dialer 1

R4(config-if)# ip address 172.16.14.1 255.255.255.252 R4(config-if)# encapsulation ppp R4(config-if)# dialer string 8140010 R4(config-if)# dialer remote-name R1

R4(config-if)# dialer pool 1 R4(config-if)# dialer-group 1

R4(config-if)# exit

R4(config)# dialer-list 2 protocol ip list 102 R4(config)# access-list 102 permit tcp any any eq smtp R4(config)# interface dialer 2

R4(config-if)# ip address 172.16.30.1 255.255.255.252 R4(config-if)# encapsulation ppp R4(config-if)# dialer string 9650001 R4(config-if)# dialer remote-name CentralOffice

R4(config-if)# dialer pool 1

R4(config-if)# dialer-group 2

R4(config-if)# exit

R4(config)# interface serial 0/0

R4(config-if)# backup interface dialer 1

© 2001, Cisco Systems, Inc. All rights reserved. Cisco CCIE Prep v1.0—Module 3-20

Next, a logical dialer interface is created. This interface will be used as a backup interface to serial 0/0. An IP address and a dialer string are assigned to the dialer interface. Interesting traffic is defined that will trigger this dialer interface. In this case, any IP traffic will bring up the link. This logical interface was specified as a member of dialer pool 1 to map it to the physical BRI 0/0 interface.

Notice that a new command has been issued on this dialer interface dialer remote-name. This command specifies the name of the device that this interface wishes to call. In this case, the opposite device has a name of R1. This remote-name is used during CHAP authentication.

In this example, you only want the dialer 1 interface to activate when your Frame Relay connection drops. To accomplish this task, dialer 1 is defined as a backup interface for serial 0/0. This configuration will allow you to have a redundant backup connection, but still use the ISDN circuit for DDR when the primary interface is functioning correctly. This configuration is impossible with Legacy DDR.

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