RIPv1有类路由的问题

    RIP实验，验证RIPv1有类别更新是否是采用接口的子网掩码为更新的子网掩码，验证方法：用3台路由器，起RIPv1，然后使用
接口IP:
r2:f0/0192.168.1.1/29

r1:s1/0192.168.1.9/29
r2:s1/0192.168.1.10/29

r1:s1/1192.168.1.17/29
r3:s1/0192.168.1.18/29

r4:f0/0192.168.1.24/29

按照上面的连接和IP地址配置每台路由器，然后启用RIPv1协议。然后在每台路由器上show ip route查看路由表。
R2#show ip route
Codes: C - connected, S - static, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     192.168.1.0/29 is subnetted, 4 subnets
C       192.168.1.8 is directly connected, Serial1/0
C       192.168.1.0 is directly connected, Ethernet0/0
R       192.168.1.24 [120/2] via 192.168.1.9, 00:00:02, Serial1/0
R       192.168.1.16 [120/1] via 192.168.1.9, 00:00:02, Serial1/0

R1#show ip route
Codes: C - connected, S - static, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     192.168.1.0/29 is subnetted, 4 subnets
C       192.168.1.8 is directly connected, Serial1/0
R       192.168.1.0 [120/1] via 192.168.1.10, 00:00:22, Serial1/0
R       192.168.1.24 [120/1] via 192.168.1.18, 00:00:21, Serial1/1
C       192.168.1.16 is directly connected, Serial1/1

R3#show ip route
Codes: C - connected, S - static, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     192.168.1.0/29 is subnetted, 4 subnets
R       192.168.1.8 [120/1] via 192.168.1.17, 00:00:12, Serial1/0
R       192.168.1.0 [120/2] via 192.168.1.17, 00:00:12, Serial1/0
C       192.168.1.24 is directly connected, Ethernet0/0
C       192.168.1.16 is directly connected, Serial1/0

可以看到，每台路由器从rip学到的路由的掩码都是29位，再看一下r2的debug信息。
R2#debug ip rip
RIP protocol debugging is on
R2#
*Mar  1 00:02:32.655: RIP: sending v1 update to 255.255.255.255 via Serial1/0 (192.168.1.10)
*Mar  1 00:02:32.655: RIP: build update entries
*Mar  1 00:02:32.655:   subnet 192.168.1.0 metric 1
*Mar  1 00:02:35.003: RIP: received v1 update from 192.168.1.9 on Serial1/0
*Mar  1 00:02:35.003:      192.168.1.16 in 1 hops
*Mar  1 00:02:35.007:      192.168.1.24 in 2 hops
*Mar  1 00:02:36.499: RIP: sending v1 update to 255.255.255.255 via Ethernet0/0 (192.168.1.1)
*Mar  1 00:02:36.499: RIP: build update entries
*Mar  1 00:02:36.499:   subnet 192.168.1.8 metric 1
*Mar  1 00:02:36.499:   subnet 192.168.1.16 metric 2
*Mar  1 00:02:36.503:   subnet 192.168.1.24 metric 3
同样也是以/29位掩码的路由信息学习和向外更新。。。。

还有R1的show ip rip database信息：
R1#show ip rip database
192.168.1.0/24    auto-summary
192.168.1.0/29
    [1] via 192.168.1.10, 00:00:04, Serial1/0
192.168.1.8/29    directly connected, Serial1/0
192.168.1.16/29    directly connected, Serial1/1
192.168.1.24/29
    [1] via 192.168.1.18, 00:00:02, Serial1/1

通过这个实验，可以让我们从原来RIPv1更新的路由只会采用默认的掩码的误区中走出来，有类路由是先根据默认掩码生成rip database，然后向外更新的时候会与接口的掩码进行最长匹配原则，然后用计算出来的那个掩码为更新时候所用的掩码。。。。