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390 Chapter 6: Routing
Figure 6-11
Auto Summarization
Notice as highlighted in Example 6-14 that Albuquerque's received update on Serial0.2 from
Seville advertises only about the entire Class A network 10.0.0.0/8 because auto summary is
enabled on Seville (by default). The IP routing table lists just one route to network 10.0.0.0.
This works fine, as long as network 10.0.0.0 is contiguous. Consider Figure 6-12, where
Example 6-14
Albuquerque's Routing Table When Seville Is Summarizing
Albuquerque#debug ip rip
02:20:42: RIP: sending v2 update to 224.0.0.9 via Serial0.2 (172.16.1.251)
02:20:42: 172.16.2.0/24 -> 0.0.0.0, metric 1, tag 0
02:20:42: RIP: sending v2 update to 224.0.0.9 via Ethernet0 (172.16.2.251)
02:20:42: 172.16.1.0/24 -> 0.0.0.0, metric 1, tag 0
02:20:42: 10.0.0.0/8 -> 0.0.0.0, metric 2, tag 0
02:20:46: RIP: received v2 update from 172.16.1.253 on Serial0.2
02:20:46: 10.0.0.0/8 -> 0.0.0.0 in 1 hops
Albuquerque#
Albuquerque#undebug all
All possible debugging has been turned off
Albuquerque#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 2 subnets
C 172.16.1.0 is directly connected, Serial0.2
C 172.16.2.0 is directly connected, Ethernet0
R 10.0.0.0/8 [120/1] via 172.16.1.253, 00:00:09, Serial0.2
172.16.2.0/24
Albuquerque
Seville
172.16.1.0/24
10.1.7.0/24
10.1.6.0/24
10.1.5.0/24
10.1.4.0/24
ch06.fm Page 390 Monday, March 20, 2000 5:11 PM