1、实验拓扑
按拓扑所示配置好OSPF后，此时由于area2与area0之间隔着area1,此时area2中的R5并没有路由可达area3、area0、area1。为此我们在R3、R4上建立一条虚链路即可。
2、实验配置
R1配置
interface Loopback0
ip address 1.1.1.1 255.255.255.0
interface Serial0/0
ip address 12.1.1.1 255.255.255.0
router ospf 110
router-id 1.1.1.1
network 1.1.1.0 0.0.0.255 area 3
network 12.1.1.0 0.0.0.255 area 3
R2配置
interface Loopback0
ip address 2.2.2.2 255.255.255.0
interface Serial0/0
ip address 12.1.1.2 255.255.255.0
interface Serial0/1
ip address 23.1.1.2 255.255.255.0
router ospf 110
router-id 2.2.2.2
network 2.2.2.0 0.0.0.255 area 0
network 12.1.1.0 0.0.0.255 area 3
network 23.1.1.0 0.0.0.255 area 0
R3配置
interface Loopback0
ip address 3.3.3.3 255.255.255.0
interface Serial0/0
ip address 34.1.1.3 255.255.255.0
interface Serial0/1
ip address 23.1.1.3 255.255.255.0
router ospf 110
router-id 3.3.3.3
network 3.3.3.0 0.0.0.255 area 0
network 23.1.1.0 0.0.0.255 area 0
network 34.1.1.0 0.0.0.255 area 1
R4配置
interface Loopback0
ip address 4.4.4.4 255.255.255.0
interface Serial0/0
ip address 34.1.1.4 255.255.255.0
interface Serial0/1
ip address 45.1.1.4 255.255.255.0
router ospf 110
router-id 4.4.4.4
log-adjacency-changes
network 4.4.4.0 0.0.0.255 area 1
network 34.1.1.0 0.0.0.255 area 1
network 45.1.1.0 0.0.0.255 area 2
R5配置
interface Loopback0
ip address 5.5.5.5 255.255.255.0
interface Serial0/1
ip address 45.1.1.5 255.255.255.0
router ospf 110
router-id 5.5.5.5
log-adjacency-changes
network 5.5.5.0 0.0.0.255 area 2
network 45.1.1.0 0.0.0.255 area 2
3、配置OSPF虚链路
此时R1和R5都没有彼此的路由。我们将R3、R4上做如下修改
R3配置
router ospf 110
area 1 virtual-link 4.4.4.4
R4配置
router ospf 110
area 1 virtual-link 3.3.3.3
