目录

一、OSPF虚链路

1.1 概念

1.2 目的：

1.3 Two common scenarios for virtual links

1.4 穿越区域的要求

1.5 实例配置

一、OSPF虚链路

1.1 概念

A virtual link is established by routing between two areas,traverse a non-backbone area,A direct logical channel is established with the backbone area

1.2 目的：

指一条通过一个非骨干区域连接到骨干区域的链路

1.3 Two common scenarios for virtual links

场景2：通过一个非骨干区域,Connect a segmented backbone area

1.4 穿越区域的要求

 虚链路必须配置在两台ABR之间

传送区域不能是末梢区域

虚链路的稳定性取决于当前区域的稳定性

虚链路还可以提供链路冗余 

1.5 实例配置

如图,Complete the above topology construction,划分网段,配置ip,宣告网段,When no virtual link is configured,R3The backbone area where it is locatedarea0 will not be able to learnarea 2的路由信息

这是因为area2No and backbone areaarea0caused by direct connection

解决办法就是在R1和R2之间即,area2inter-area routing and area0The inter-area route is used as a virtual link

Steps for establishing a virtual link

Get the route between two areasRouter-ID

可以从邻居的方法来获取.可以说,路由器ID就是接口的ID

这里是R1和R2建立虚链路

在R1上配置Area 1 (traversed area) virtual-link router-id（R2）

在R0query its neighbors,就可以获取R2的router-id

show ip ospf neighbor

由此得到R2的router-id为40.0.0.1

R2上配置

Router(config-router)#area 1 virtual-link 20.0.0.1

Router(config-router)#

00:26:31: %OSPF-5-ADJCHG: Process 1, Nbr 20.0.0.1 on OSPF_VL0 from LOADING to FULL, Loading Done

R1上配置

Router(config-router)#area 1 virtual-link 40.0.0.1

Router(config-router)#

00:26:34: %OSPF-5-ADJCHG: Process 1, Nbr 40.0.0.1 on OSPF_VL0 from LOADING to FULL, Loading Done

Query virtual link configuration information

Router#show ip ospf virtual-links

查看R3路由表

The physical link is down,The virtual link does not exist,Virtual links rely on physical links