第一步、预配置
r1(config)#int s3/0
r1(config-if)#ip add 123.0.0.1 255.255.255.0
r1(config-if)#no sh
r1(config-if)#int lo0
r1(config-if)#ip add 1.1.1.1 255.255.255.0
r1(config-if)#exit

r2(config)#int s3/0
r2(config-if)#ip add 123.0.0.2 255.255.255.0
r2(config-if)#no sh
r2(config-if)#int lo0
r2(config-if)#ip add 2.2.2.2 255.255.255.0
r2(config-if)#exit

r3(config)#int s3/0
r3(config-if)#ip add 123.0.0.3 255.255.255.0
r3(config-if)#int lo0
r3(config-if)#ip add 3.3.3.3 255.255.255.0
r3(config-if)#exit


第二步、配置帧中继
r1(config)#int s3/0
r1(config-if)#en fr
r1(config-if)#no frame-relay inv
r1(config-if)#frame-relay map ip 123.0.0.2 102 broadcast
r1(config-if)#frame-relay map ip 123.0.0.3 103 broadcast

r2(config)#int s3/0
r2(config-if)#en fr
r2(config-if)#no frame-relay inverse-arp
r2(config-if)#frame-relay map ip 123.0.0.1 201 b
r2(config-if)#frame-relay map ip 123.0.0.3 201 b

r3(config)#int s3/0
r3(config-if)#en fr
r3(config-if)#no frame-relay inv
r3(config-if)#frame-relay map ip 123.0.0.1 301 b
r3(config-if)#frame-relay map ip 123.0.0.2 301 b

第三步、配置ospf
r1(config)#router ospf 1
r1(config-router)#net 123.0.0.1 0.0.0.0 a 0
r1(config-router)#net 1.1.1.1 0.0.0.0 a 0
r1(config-router)#end

r2(config)#router ospf 1
r2(config-router)#net 123.0.0.2 0.0.0.0 a 0
r2(config-router)#net 2.2.2.2 0.0.0.0 a 0
r2(config-router)#end

r3(config)#router ospf 1
r3(config-router)#net 123.0.0.3 0.0.0.0 a 0
r3(config-router)#net 3.3.3.3 0.0.0.0 a 0
r3(config-router)#end

第四步、修改接口优先级
r2(config)#int s3/0
r2(config-if)#ip o priority 0
r2(config-if)#end

r3(config)#int s3/0
r3(config-if)#ip o priority 0
r3(config-if)#end
确保r1为DR

第五步、修改接口类型、hello时间
r1(config)#int s3/0
r1(config-if)#ip o network broadcast
r1(config-if)#ip o hello-interval 30
r1(config-if)#end

第六步、查看路由表
r1#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

1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/65] via 123.0.0.2, 00:00:02, Serial3/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/65] via 123.0.0.3, 00:00:02, Serial3/0
123.0.0.0/24 is subnetted, 1 subnets
C 123.0.0.0 is directly connected, Serial3/0

r2#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

1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/65] via 123.0.0.1, 00:07:51, Serial3/0
2.0.0.0/24 is subnetted, 1 subnets
C 2.2.2.0 is directly connected, Loopback0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/65] via 123.0.0.3, 00:07:51, Serial3/0
123.0.0.0/24 is subnetted, 1 subnets
C 123.0.0.0 is directly connected, Serial3/0

r3#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

1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/65] via 123.0.0.1, 00:08:11, Serial3/0
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/65] via 123.0.0.2, 00:08:11, Serial3/0
3.0.0.0/24 is subnetted, 1 subnets
C 3.3.3.0 is directly connected, Loopback0
123.0.0.0/24 is subnetted, 1 subnets
C 123.0.0.0 is directly connected, Serial3/0