根据拓扑图可看到区域1与骨干区域0直接相连而区域2与骨干区域没有直接相连，这种情况下我们可以创建一条虚链路使区域2与骨干区域0直接相连。虚链路还可将不连续的区域0连接起来。

 R1配置：

interface Loopback1

 ip address 1.1.1.1 255.255.255.255

!

interface Serial1/1

 ip address 12.12.12.1 255.255.255.0

 serial restart-delay 0

!

router ospf 1

 router-id 1.1.1.1

 log-adjacency-changes

 network 1.1.1.0 0.0.0.255 area 0

 network 12.12.12.0 0.0.0.255 area 0

!

R2配置：

interface Loopback1

 ip address 2.2.2.2 255.255.255.0

!

interface Serial1/0

 ip address 12.12.12.2 255.255.255.0

 serial restart-delay 0

!

interface Serial1/1

 ip address 23.23.23.2 255.255.255.0

 serial restart-delay 0

!

router ospf 1

 router-id 2.2.2.2

 log-adjacency-changes

 area 1 virtual-link 4.4.4.4

 network 2.2.2.0 0.0.0.255 area 0

 network 12.12.12.0 0.0.0.255 area 0

 network 23.23.23.0 0.0.0.255 area 1

!

R3配置：

interface Loopback1

 ip address 3.3.3.3 255.255.255.255

!

interface Serial1/0

 ip address 23.23.23.3 255.255.255.0

 serial restart-delay 0

!

interface Serial1/1

 ip address 34.34.34.3 255.255.255.0

 serial restart-delay 0

!

router ospf 1

 router-id 3.3.3.3

 log-adjacency-changes

 network 3.3.3.0 0.0.0.255 area 1

 network 23.23.23.0 0.0.0.255 area 1

 network 34.34.34.0 0.0.0.255 area 1

!

R4配置：

interface Loopback1

 ip address 4.4.4.4 255.255.255.0

!

interface Serial1/0

 ip address 34.34.34.4 255.255.255.0

 serial restart-delay 0

!

interface Serial1/1

 ip address 45.45.45.4 255.255.255.0

 serial restart-delay 0

!

router ospf 1

 router-id 4.4.4.4

 log-adjacency-changes

 area 1 virtual-link 2.2.2.2

 network 4.4.4.0 0.0.0.255 area 1

 network 34.34.34.0 0.0.0.255 area 1

 network 45.45.45.0 0.0.0.255 area 2

!

R5配置：

interface Loopback1

 ip address 5.5.5.5 255.255.255.0

!

interface Serial1/0

 ip address 45.45.45.5 255.255.255.0

 serial restart-delay 0

!

router ospf 1

 router-id 5.5.5.5

 log-adjacency-changes

 network 5.5.5.0 0.0.0.255 area 2

 network 45.45.45.0 0.0.0.255 area 2

!

配置虚链路后再次查看R1的路由表，已经学到了区域2的路由：

Router#show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     34.0.0.0/24 is subnetted, 1 subnets

O IA    34.34.34.0 [110/192] via 12.12.12.2, 00:08:26, Serial1/1

     1.0.0.0/32 is subnetted, 1 subnets

C       1.1.1.1 is directly connected, Loopback1

     2.0.0.0/32 is subnetted, 1 subnets

O       2.2.2.2 [110/65] via 12.12.12.2, 00:08:26, Serial1/1

     3.0.0.0/32 is subnetted, 1 subnets

O IA    3.3.3.3 [110/129] via 12.12.12.2, 00:08:26, Serial1/1

     4.0.0.0/32 is subnetted, 1 subnets

O IA    4.4.4.4 [110/193] via 12.12.12.2, 00:08:26, Serial1/1

     5.0.0.0/32 is subnetted, 1 subnets

O IA    5.5.5.5 [110/257] via 12.12.12.2, 00:08:26, Serial1/1  //区域2路由

     23.0.0.0/24 is subnetted, 1 subnets

O IA    23.23.23.0 [110/128] via 12.12.12.2, 00:08:27, Serial1/1

     12.0.0.0/24 is subnetted, 1 subnets

C       12.12.12.0 is directly connected, Serial1/1

     45.0.0.0/24 is subnetted, 1 subnets

O IA    45.45.45.0 [110/256] via 12.12.12.2, 00:08:27, Serial1/1          //区域2路由

在末配置虚链路时查看R1的路由表，R1是学不到区域2的路由

Router#show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     34.0.0.0/24 is subnetted, 1 subnets

O IA    34.34.34.0 [110/192] via 12.12.12.2, 00:12:49, Serial1/1

     1.0.0.0/32 is subnetted, 1 subnets

C       1.1.1.1 is directly connected, Loopback1

     2.0.0.0/32 is subnetted, 1 subnets

O       2.2.2.2 [110/65] via 12.12.12.2, 00:12:49, Serial1/1

     3.0.0.0/32 is subnetted, 1 subnets

O IA    3.3.3.3 [110/129] via 12.12.12.2, 00:12:49, Serial1/1

     4.0.0.0/32 is subnetted, 1 subnets

O IA    4.4.4.4 [110/193] via 12.12.12.2, 00:12:49, Serial1/1

     23.0.0.0/24 is subnetted, 1 subnets

O IA    23.23.23.0 [110/128] via 12.12.12.2, 00:12:49, Serial1/1

     12.0.0.0/24 is subnetted, 1 subnets

C       12.12.12.0 is directly connected, Serial1/1