用模拟器做 帧中继上的RIP出现的问题
模拟器使用dynamips 的GNS3
IOS使用c2691-advsecurityk9-mz.124-11.T2.bin
拓扑如下:
只做了R1-R3 R1-R4 这2条DLCI R3-R4没有DLCI
R2模拟帧中继交换机
在做RIP前.网络正常.做RIP后检查路由表.发现非常不正常.
R1路由表:
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Serial0/0
R 33.0.0.0/8 [120/1] via 1.1.1.4, 00:00:06, Serial0/0
[120/1] via 1.1.1.3, 00:00:08, Serial0/0
11.0.0.0/24 is subnetted, 1 subnets
C 11.11.11.0 is directly connected, Loopback0
R 44.0.0.0/8 [120/1] via 1.1.1.4, 00:00:06, Serial0/0
[120/1] via 1.1.1.3, 00:00:08, Serial0/0
R1#
在R1上竟然出现了2条负载均衡,而且R3-R4是没有DLCI的,到达R4不可能经过R3.到达R3不可能经过R4.
即使是认为到达R4能走R3.那也不可能是负载均衡.跳数是2,不可能是1.
重新配置RIP,帧中继,都无法解决,想到会不会是RIPV1对这些公网地址支持不好,就改为RIPV2测试.
这是R1真的正常起来了
R1:
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Serial0/0
33.0.0.0/24 is subnetted, 1 subnets
R 33.33.33.0 [120/1] via 1.1.1.3, 00:00:07, Serial0/0
11.0.0.0/24 is subnetted, 1 subnets
C 11.11.11.0 is directly connected, Loopback0
44.0.0.0/24 is subnetted, 1 subnets
R 44.44.44.0 [120/1] via 1.1.1.4, 00:00:07, Serial0/0
但是R3.R4却出现问题
R3
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Serial0/1
33.0.0.0/24 is subnetted, 1 subnets
C 33.33.33.0 is directly connected, Loopback0
11.0.0.0/24 is subnetted, 1 subnets
R 11.11.11.0 [120/1] via 1.1.1.1, 00:00:23, Serial0/1
44.0.0.0/24 is subnetted, 1 subnets
R 44.44.44.0 [120/2] via 1.1.1.4, 00:00:23, Serial0/1
R3#
R4
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Serial0/1
33.0.0.0/24 is subnetted, 1 subnets
R 33.33.33.0 [120/2] via 1.1.1.3, 00:00:02, Serial0/1
11.0.0.0/24 is subnetted, 1 subnets
R 11.11.11.0 [120/1] via 1.1.1.1, 00:00:02, Serial0/1
44.0.0.0/24 is subnetted, 1 subnets
C 44.44.44.0 is directly connected, Loopback0
R4#
44.0.0.0/24 is subnetted, 1 subnets
R 44.44.44.0 [120/2] via 1.1.1.4, 00:00:23, Serial0/1
到达44.0.0.0 出现了经过1.1.1.4到达.但帧中继里面R3跟R4不是直连的,路由器却认为是直连,更奇怪的是跳数竟然为2,既然经过1.1.14到达.跳数应该为1才正常.
最后怀疑到RIP的更新包有问题.
在R3上debug ip rip 查看到
*Mar 1 00:02:36.775: RIP: received v1 update from 1.1.1.1 on Serial0/1
*Mar 1 00:02:36.775: 1.1.1.0 in 1 hops
*Mar 1 00:02:36.779: 11.0.0.0 in 1 hops
*Mar 1 00:02:36.783: 44.0.0.0 in 1 hops
R3#
*Mar 1 00:02:38.783: RIP: sending v1 flash update to 255.255.255.255 via Serial0/1 (1.1.1.3)
*Mar 1 00:02:38.787: RIP: build flash update entries
*Mar 1 00:02:38.787: network 11.0.0.0 metric 1
*Mar 1 00:02:38.791: network 44.0.0.0 metric 1
答案出现了.R3收到R1的更新后,却没有更改跳数.直接就发回给R1(帧中继默认关闭水平分割,所以可以由R3返回通过R1学习到的路由信息)
最后更换了7200的IOS.一切正常,问题应该是2691这个IOS引起.在帧中继下路由协议有问题.大家做帧中继实验时避免使用这个IOS