Figure 75 Discontiguous Networks Across Multiple Interfaces

The routing table for R1 in Figure 7-5 would be as follows:

131.108.0.0/16 is variably subnetted, 2 subnets, 2 masks

R 131.108.0.0/16 [120/1] via 140.10.10.9, 00:00:24, Serial 2/0

R 131.108.0.0/16 [120/1] via 140.10.10.5, 00:00:02, Serial 3/0

C 131.108.10.0/24 is directly connected, Ethernet3/0

C 140.10.10.8/30 is directly connected, Serial 2/0

C 140.10.10.4/30 is directly connected, Serial 3/0.

To solve the problem shown in Figure 7-5, you must disable auto-summary. This command, which tells the router to stop creating summarized routes when crossing a major net route, must be entered on all the routers. (In Figure 7-5, this command must be entered on R2 and R3.)

The configuration for R1 is as follows:

router rip network 131.108.0.0 network 140.10.0.0 no auto-summary

Configuration for R2 router rip network 131.108.0.0 network 140.10.0.0 no auto-summary

The configuration for R3 would be as follows:

router rip network 131.108.0.0 140.10.0.0 no auto-summary

Routing table for R1 then changes to: 131.108.0.0/24 is subnetted, 3 subnets

R 131.108.20.0/24 [120/1] via 140.10.10.9, 00:00:24, Serial 2/0

R 131.108.30.0/24 [120/1] via 140.10.10.5, 00:00:02, Serial 3/0

C 131.108.10.0/24 is directly connected, Ethernet3/0

C 140.10.10.8/30 is directly connected, Serial 2/0

C 140.10.10.4/30 is directly connected, Serial 3/0.

With auto-summary disabled, R1 has the correct next-hop field for each destination.

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