Cisco IOS Cookbook, 2nd Edition

Putting It All Together

Problem

You want to combine all of best the elements in this chapter to create a good redundant ISP connection.

Solution

For simplicity, we will extend the single router dual ISP configuration of Recipe 9.4 rather than the dual router dual ISP example of Recipe 9.5. It should be clear from the discussion in Recipe 9.5 how to extend this example to the two-router case:

Router1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#interface Serial0
Router1(config-if)#description connection to ISP #1, ASN 65510
Router1(config-if)#ip address 192.168.1.6 255.255.255.252
Router1(config-if)#exit
Router1(config)#interface Serial1
Router1(config-if)#description connection to ISP #2, ASN 65520
Router1(config-if)#ip address 192.168.2.6 255.255.255.252
Router1(config-if)#exit
Router1(config)#interface Ethernet0
Router1(config-if)#description connection to internal network, ASN 65500
Router1(config-if)#ip address 172.18.5.2 255.255.255.0
Router1(config-if)#exit
Router1(config)#ip as-path access-list 15 permit ^$
Router1(config)#ip route 0.0.0.0 0.0.0.0 192.168.101.0 1
Router1(config)#ip route 0.0.0.0 0.0.0.0 192.168.102.0 2
Router1(config)#ip prefix-list CREATE-DEFAULT seq 10 permit 192.168.101.0/24
Router1(config)#ip prefix-list CREATE-DEFAULT seq 20 permit 192.168.102.0/24
Router1(config)#ip prefix-list BLOCK-DEFAULT seq 10 permit 0.0.0.0/0 ge 1
Router1(config)#route-map PREPEND permit 10
Router1(config-route-map)#set as-path prepend ...