模拟器使用dynamips 的GNS3

IOS使用c2691-advsecurityk9-mz.124-11.T2.bin

 

拓扑如下:

 

image 

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