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Cisco IOS Cookbook, 2nd Edition by Ian Brown, Kevin Dooley

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Automating Dial Backup

Problem

You want automatic dial recovery in case a WAN link fails.

Solution

One of the most reliable ways of implementing dial backup on a Cisco router is to use a floating static default route, as follows:

Router1#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#interface BRI0/0
Router1(config-if)#ip address 10.1.99.55 255.255.255.0
Router1(config-if)#encapsulation ppp
Router1(config-if)#dialer idle-timeout 300
Router1(config-if)#dialer map ip 10.1.99.1 name dialhost broadcast 95551212
Router1(config-if)#dialer load-threshold 50 either
Router1(config-if)#dialer-group 1
Router1(config-if)#isdn switch-type basic-ni
Router1(config-if)#isdn spid1 800555123400 5551234
Router1(config-if)#isdn spid2 800555123500 5551235
Router1(config-if)#ppp authentication chap
Router1(config-if)#ppp multilink
Router1(config-if)#exit
Router1(config)#username dialhost password dialpassword
Router1(config)#ip route 0.0.0.0 0.0.0.0 10.1.99.1 180
Router1(config)#dialer-list 1 protocol ip list 101
Router1(config)#access-list 101 deny eigrp any any
Router1(config)#access-list 101 permit ip any any
Router1(config)#router eigrp 55
Router1(config-router)#network 10.0.0.0
Router1(config-router)#end
Router1#

Then the matching configuration of the other end is shown in Recipe 13.2.

Discussion

This recipe includes several important features. First, notice that we have configured dial backup using an ISDN BRI interface on this router. So we have to set ...

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