一个简单地次优路径小实验

基本配置

R1：

interface FastEthernet0/0

 ip address 12.12.12.1 255.255.255.0

 duplex auto

 speed auto

interface FastEthernet0/1

 ip address 13.13.13.1 255.255.255.0

 duplex auto

 speed auto

router eigrp 123

 network 12.12.12.1 0.0.0.0

 network 13.13.13.1 0.0.0.0

 no auto-summary

 

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R2：

interface Loopback0

 ip address 2.2.2.2 255.255.255.0

 ip ospf network point-to-point

interface FastEthernet0/0

 ip address 12.12.12.2 255.255.255.0

 duplex auto

 speed auto

interface FastEthernet0/1

 ip address 23.23.23.2 255.255.255.0

 duplex auto

 speed auto

router eigrp 123

 network 2.2.2.2 0.0.0.0

 network 12.12.12.2 0.0.0.0

 no auto-summary

router ospf 1

 log-adjacency-changes

 network 2.2.2.2 0.0.0.0 area 0

 network 23.23.23.2 0.0.0.0 area 0

 

------------------------------------------------

R3:

interface Loopback0

 ip address 3.3.3.3 255.255.255.0

 ip ospf network point-to-point

interface FastEthernet0/0

 ip address 13.13.13.3 255.255.255.0

 duplex auto

 speed auto

interface FastEthernet0/1

 ip address 23.23.23.3 255.255.255.0

 duplex auto

 speed auto

router eigrp 123

 network 3.3.3.3 0.0.0.0

 network 13.13.13.3 0.0.0.0

 no auto-summary

router ospf 1

 log-adjacency-changes

 network 3.3.3.3 0.0.0.0 area 0

 network 23.23.23.3 0.0.0.0 area 0

 

配完后，我们看R2的路由表：

R2#sh ip route | in 3.3.3.0

D       3.3.3.0 [90/435200] via 12.12.12.1, 00:05:04, FastEthernet0/0

同样的，R3上：

R3#sh ip route | in 2.2.2.0

D       2.2.2.0 [90/435200] via 13.13.13.1, 00:05:20, FastEthernet0/0

可以很明显地看到两条次优：

R2到达R3的loopback0口选择了EIGRP路由，从R1绕，R3到R2loopback0口也是一样，原因很好分析， 因为EIGRP的内部管理距离90优于OSPF的110。

因此解决方案就是改变管理距离：

这里可能有人会过滤，但是过滤了EIGRP的路由就不冗余了。

R2

ip access-list standard R3LOOPBACK

 permit 3.3.3.0 0.0.0.255

router ospf 1

 distance 89 3.3.3.3 0.0.0.0 R3LOOPBACK

 

R3

ip access-list standard R2LOOPBACK

 permit 2.2.2.0 0.0.0.255

router ospf 1

 distance 89 2.2.2.2 0.0.0.0 R2LOOPBACK

配置结束后再看路由表

R2#sh ip route | in 3.3.3.0

O       3.3.3.0 [89/11] via 23.23.23.3, 00:10:24, FastEthernet0/1

R3#sh ip route | in 2.2.2.0

O       2.2.2.0 [89/11] via 23.23.23.2, 00:03:19, FastEthernet0/1