如下图示：
R1: interface Loopback0 ip address 1.1.1.1 255.255.255.255 ip ospf 1 area 2 interface FastEthernet0/0 ip address 12.1.1.1 255.255.255.0 ip ospf 1 area 2 no sh router ospf 1 router-id 1.1.1.1 network 1.1.1.1 0.0.0.0 area 2 network 12.1.1.0 0.0.0.255 area 2 R2: interface Loopback0 ip address 2.2.2.2 255.255.255.255 ip ospf 1 area 0 interface FastEthernet0/0 ip address 12.1.1.2 255.255.255.0 ip ospf 1 area 2 no sh interface FastEthernet0/1 ip address 24.1.1.2 255.255.255.0 ip ospf 1 area 2 no sh interface Serial1/0 ip address 23.1.1.2 255.255.255.0 ip ospf 1 area 0 no sh router ospf 1 network 2.2.2.2 0.0.0.0 area 0 network 12.1.1.0 0.0.0.255 area 2 network 23.1.1.0 0.0.0.255 area 0 network 24.1.1.0 0.0.0.255 area 2 R3: interface Loopback0 ip address 3.3.3.3 255.255.255.255 ip ospf 1 area 0 interface Serial1/0 ip address 23.1.1.3 255.255.255.0 ip ospf 1 area 0 no sh router ospf 1 router-id 3.3.3.3 network 3.3.3.3 0.0.0.0 area 0 network 23.1.1.0 0.0.0.255 area 0 R4: interface Loopback0 ip address 4.4.4.4 255.255.255.255 ip ospf 1 area 2 interface FastEthernet0/1 ip address 24.1.1.4 255.255.255.0 ip ospf 1 area 2
no sh
router ospf 1 router-id 4.4.4.4 network 4.4.4.4 0.0.0.0 area 2 network 24.1.1.0 0.0.0.255 area 2
