RIP出现/32主机路由情况以及解决
R1配置：
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
192.168.1.0/28 is subnetted, 2 subnets
C 192.168.1.32 is directly connected, Serial1/0
R 192.168.1.16 [120/1] via 192.168.1.34, 00:00:24, Serial1/0
R2配置：
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
192.168.1.0/28 is subnetted, 2 subnets
C 192.168.1.32 is directly connected, Serial2/0
C 192.168.1.16 is directly connected, Serial1/0
R3配置：
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
192.168.1.0/28 is subnetted, 2 subnets
R 192.168.1.32 [120/1] via 192.168.1.17, 00:00:18, Serial1/0
C 192.168.1.16 is directly connected, Serial1/0
R1配置：
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
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.32/27 is directly connected, Serial1/0
R 192.168.1.16/32 [120/1] via 192.168.1.34, 00:00:06, Serial1/0
R1#
R1#debug ip rip database
RIP database events debugging is on
R1#
*Mar 1 00:39:58.263: RIP-DB: network_update with 192.168.1.16/24 succeeds
*Mar 1 00:39:58.263: RIP-DB: adding 192.168.1.16/0 (metric 1) via 192.168.1.34 on Serial1/0 to RIP database
在RIP中
(1) 如果接口的IP地址是在相同的主类网络子网中，子网掩码不一致，会导致路由信息发布失败。
(2) 如果接口的IP地址是在不同的主类网络子网中，子网掩码不一致，路由通告正常，且正常汇总。
Ａ、如果在同一主网的子网通告，采用接收接口的掩码更新安装进路由表，如果收到子网通告主机位不为零，则以／３２主机路由方式安装进路由表，并通告给下一跳路由器。
Ｂ、如果在不同主网的子网通告，如果在路由表里已经存在对应子网，则忽略改更新。如果在路由表里不存在，则以主类网络号安装进路由表，或者以／３２主机路有的方式安装进路由表（当接收接口为unnumbered link 时）。出现／３２为主机路由一共是以上２种可能。
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