实验需求
3、当R2、R3之间的链路故障时,R1访问R5下属LOOPBACK的流量自动切换为经R2、R4、R5且往返路径一致
R2、R3之间链路down掉,来自R5的172.16.65.0/24的汇总路由将没有
指浮动静态路由
R2(config)#ip route 172.16.0.0 255.255.0.0 s1/1 125
R1#trac 172.16.65.1
Type escape sequence to abort.
Tracing the route to 172.16.65.1
1 * * *
2 * //通不了
在R4配静态指R5的三个网段并重发布
ip route 172.16.65.0 255.255.255.0 192.168.100.5
ip route 172.16.66.0 255.255.255.0 192.168.100.5
ip route 172.16.67.0 255.255.255.0 192.168.100.5
redistribute static subnets
当R2、R3之间链路恢复,RIP的AD值比OSPF的AD值大,R2展示OSPF来的路由,不符合要求
用最长匹配
在上面的链路用明细,下面的链路用汇总
R4(config)#ip route 172.16.64.0 255.255.252.0 f0/0
R4(config-router)#redistribute static subnets
R2上路由表如下(以下R2、R3之间还没有down、省略)
172.16.0.0/16 is variably subnetted, 3 subnets, 3 masks
R 172.16.0.0/16 [120/3] via 192.168.23.3, 00:00:10, Serial1/0 <-------
D 172.16.1.0/24 [90/409600] via 192.168.12.1, 00:03:20, FastEthernet0/0
O E2 172.16.64.0/22 [110/20] via 192.168.24.4, 00:01:41, Serial1/1 <-----
R 192.168.100.0/24 [120/1] via 192.168.23.3, 00:00:10, Serial1/0
关闭R5的自动汇总
172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks
D 172.16.1.0/24 [90/409600] via 192.168.12.1, 00:07:37, FastEthernet0/0
O E2 172.16.64.0/22 [110/20] via 192.168.24.4, 00:07:37, Serial1/1
R 172.16.65.0/24 [120/3] via 192.168.23.3, 00:00:09, Serial1/0
R 172.16.66.0/24 [120/3] via 192.168.23.3, 00:00:09, Serial1/0
R 172.16.67.0/24 [120/3] via 192.168.23.3, 00:00:11, Serial1/0
R 192.168.100.0/24 [120/1] via 192.168.23.3, 00:00:11, Serial1/0
//可以看到172.16.0.0/16没了
正常情况下去往172.16.65.1该怎么走呢?R2上面有条/22的汇总可以去往172.16.65.1,而又有条172.16.65.0/24的明细路由,那么毫无疑问,走的是明细,也就是上面的链路。(最长匹配)
那么让R2、R3之间的链路down掉
R2路由表如下(省略)
172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
D 172.16.1.0/24 [90/409600] via 192.168.12.1, 00:03:52, FastEthernet0/0
O E2 172.16.64.0/22 [110/20] via 192.168.24.4, 00:03:52, Serial1/1
R2上有去往R5的三个网段的汇总路由,指向R4。而汇总是从R4重发布静态进OSPF的,指向R5的三个网段。而R2与R3之间的链路down掉,导致R5没有去往192.168.12.0/24和172.16.1.0/24的路由,还有192.168.24.0/24
在R5配浮动静态路由(要使R5在正常情况下走上面的链路)
ip route 172.16.1.0 255.255.255.0 192.168.100.4 125
ip route 192.168.12.0 255.255.255.0 192.168.100.4 125
ip route 192.168.24.0 255.255.255.0 192.168.100.4
验证之后R1去往R5没问题,可R5去往R1就出现超时,原因是R1和R2上面没有192.168.100.0/24的路由
在R4上重发布直连(让R2、R1学到192.168.100.0/24)
R4(config-router)#redistribute connected subnets
验证成功