解决OSPF 孤岛问题_ospf
 
 
 
     不建立 virtual-link 以前配置及路由表
 
r1 配置
router>en
router#conf t
router(config)#host r1
r1(config)#no ip domain-lookup
r1(config)#ena sec 123
r1(config)#ban mot #Welcome to r1#
r1(config)#line vty 0 4
r1(config-line)#no login
r1(config-line)#line con 0
r1(config-line)#no exec-timeout
r1(config-line)#int lo0
r1(config-if)#ip add 1.1.1.1 255.255.255.255
r1(config-if)#des router-id
r1(config-if)#int f 0/0
r1(config-if)#ip add 192.168.3.2 255.255.255.0
r1(config-if)#des link to r2
r1(config-if)#no shut
r1(config-if)#router ospf 1
r1(config-router)#router-id 1.1.1.1
r1(config-router)#net 192.168.3.0 0.0.0.255 area 0
r1(config-router)#net 1.1.1.1 0.0.0.0 area 0
r1(config-router)#end
r1#
r2 配置
router>en
router#conf t
router(config)#host r2
r2(config)#no ip domain-lookup
r2(config)#ena sec 123
r2(config)#ban mot #Welcome to r2#
r2(config)#line vty 0 4
r2(config-line)#no login
r2(config-line)#line con 0
r2(config-line)#no exec-timeout
r2(config-line)#int lo0
r2(config-if)#ip add 2.2.2.2 255.255.255.255
r2(config-if)#des router-id
r2(config-if)#int f 0/0
r2(config-if)#ip add 192.168.2.2 255.255.255.0
r2(config-if)#des link to r3
r2(config-if)#no shut
r2(config-if)#int f 1/0
r2(config-if)#ip add 192.168.3.1 255.255.255.0
r2(config-if)#des link to r1
r2(config-if)#no shut
r2(config-if)#router ospf 1
r2(config-router)#router-id 2.2.2.2
r2(config-router)#net 192.168.3.0 0.0.0.255 area 0
r2(config-router)#net 192.168.2.0 0.0.0.255 area 2
r2(config-router)#net 2.2.2.2 0.0.0.0 area 0
r2(config-router)#end
r2#
r3 配置
router>en
router#conf t
router(config)#host r3
r3(config)#no ip domain-lookup
r3(config)#ena sec 123
r3(config)#ban mot #Welcome to r3#
r3(config)#line vty 0 4
r3(config-line)#no login
r3(config-line)#line con 0
r3(config-line)#no exec-timeout
r3(config-line)#int lo0
r3(config-if)#ip add 3.3.3.3 255.255.255.255
r3(config-if)#des router-id
r3(config-if)#int f 0/0
r3(config-if)#ip add 192.168.1.2 255.255.255.0
r3(config-if)#des link to r4
r3(config-if)#no shut
r3(config-if)#int f 1/0
r3(config-if)#ip add 192.168.2.1 255.255.255.0
r3(config-if)#des link to r2
r3(config-if)#no shut
r3(config-if)#router ospf 1
r3(config-router)#router-id 3.3.3.3
r3(config-router)#net 192.168.1.0 0.0.0.255 area 4
r3(config-router)#net 192.168.2.0 0.0.0.255 area 2
r3(config-router)#net 3.3.3.3 0.0.0.0 area 2
r3(config-router)#end
r3#
r1 配置
router>en
router#conf t
router(config)#host r4
r4(config)#no ip domain-lookup
r4(config)#ena sec 123
r4(config)#ban mot #Welcome to r4#
r4(config)#line vty 0 4
r4(config-line)#no login
r4(config-line)#line con 0
r4(config-line)#no exec-timeout
r4(config-line)#int lo0
r4(config-if)#ip add 4.4.4.4 255.255.255.255
r4(config-if)#des router-id
r4(config-if)#int f 0/0
r4(config-if)#ip add 192.168.1.1 255.255.255.0
r4(config-if)#des link to r3
r4(config-if)#no shut
r4(config-if)#router ospf 1
r4(config-router)#router-id 4.4.4.4
r4(config-router)#net 192.168.1.0 0.0.0.255 area 4
r4(config-router)#net 4.4.4.4 0.0.0.0 area 4
r4(config-router)#end
r4#
 r1 无法获取r4 的路由信息
 
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
     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback0
     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/2] via 192.168.3.1, 00:00:00, FastEthernet0/0
     3.0.0.0/32 is subnetted, 1 subnets
O IA    3.3.3.3 [110/3] via 192.168.3.1, 00:00:00, FastEthernet0/0
O IA 192.168.2.0/24 [110/2] via 192.168.3.1, 00:00:00, FastEthernet0/0
C    192.168.3.0/24 is directly connected, FastEthernet0/0

  r4 什么也看不到
 
r4#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
     4.0.0.0/32 is subnetted, 1 subnets
C       4.4.4.4 is directly connected, Loopback0
C    192.168.1.0/24 is directly connected, FastEthernet0/0
 
 建立虚链路以后的配置与路由表
 
 
r1 配置
router>en
router#conf t
router(config)#host r1
r1(config)#no ip domain-lookup
r1(config)#ena sec 123
r1(config)#ban mot #Welcome to r1#
r1(config)#line vty 0 4
r1(config-line)#no login
r1(config-line)#line con 0
r1(config-line)#no exec-timeout
r1(config-line)#int lo0
r1(config-if)#ip add 1.1.1.1 255.255.255.255
r1(config-if)#des router-id
r1(config-if)#int f 0/0
r1(config-if)#ip add 192.168.3.2 255.255.255.0
r1(config-if)#des link to r2
r1(config-if)#no shut
r1(config-if)#router ospf 1
r1(config-router)#router-id 1.1.1.1
r1(config-router)#net 192.168.3.0 0.0.0.255 area 0
r1(config-router)#net 1.1.1.1 0.0.0.0 area 0
r1(config-router)#end
r1#
r2 配置
router>en
router#conf t
router(config)#host r2
r2(config)#no ip domain-lookup
r2(config)#ena sec 123
r2(config)#ban mot #Welcome to r2#
r2(config)#line vty 0 4
r2(config-line)#no login
r2(config-line)#line con 0
r2(config-line)#no exec-timeout
r2(config-line)#int lo0
r2(config-if)#ip add 2.2.2.2 255.255.255.255
r2(config-if)#des router-id
r2(config-if)#int f 0/0
r2(config-if)#ip add 192.168.2.2 255.255.255.0
r2(config-if)#des link to r3
r2(config-if)#no shut
r2(config-if)#int f 1/0
r2(config-if)#ip add 192.168.3.1 255.255.255.0
r2(config-if)#des link to r1
r2(config-if)#no shut
r2(config-if)#router ospf 1
r2(config-router)#router-id 2.2.2.2
r2(config-router)#net 192.168.3.0 0.0.0.255 area 0
r2(config-router)#net 192.168.2.0 0.0.0.255 area 2
r2(config-router)#net 2.2.2.2 0.0.0.0 area 0
r2(config-router)#area 2 virtual-link 3.3.3.3
r2(config-router)#end
r2#
r3 配置
router>en
router#conf t
router(config)#host r3
r3(config)#no ip domain-lookup
r3(config)#ena sec 123
r3(config)#ban mot #Welcome to r3#
r3(config)#line vty 0 4
r3(config-line)#no login
r3(config-line)#line con 0
r3(config-line)#no exec-timeout
r3(config-line)#int lo0
r3(config-if)#ip add 3.3.3.3 255.255.255.255
r3(config-if)#des router-id
r3(config-if)#int f 0/0
r3(config-if)#ip add 192.168.1.2 255.255.255.0
r3(config-if)#des link to r4
r3(config-if)#no shut
r3(config-if)#int f 1/0
r3(config-if)#ip add 192.168.2.1 255.255.255.0
r3(config-if)#des link to r2
r3(config-if)#no shut
r3(config-if)#router ospf 1
r3(config-router)#router-id 3.3.3.3
r3(config-router)#net 192.168.1.0 0.0.0.255 area 4
r3(config-router)#net 192.168.2.0 0.0.0.255 area 2
r3(config-router)#net 3.3.3.3 0.0.0.0 area 2
r3(config-router)#area 2 virtual-link 2.2.2.2
r3(config-router)#end
r3#
r1 配置
router>en
router#conf t
router(config)#host r4
r4(config)#no ip domain-lookup
r4(config)#ena sec 123
r4(config)#ban mot #Welcome to r4#
r4(config)#line vty 0 4
r4(config-line)#no login
r4(config-line)#line con 0
r4(config-line)#no exec-timeout
r4(config-line)#int lo0
r4(config-if)#ip add 4.4.4.4 255.255.255.255
r4(config-if)#des router-id
r4(config-if)#int f 0/0
r4(config-if)#ip add 192.168.1.1 255.255.255.0
r4(config-if)#des link to r3
r4(config-if)#no shut
r4(config-if)#router ospf 1
r4(config-router)#router-id 4.4.4.4
r4(config-router)#net 192.168.1.0 0.0.0.255 area 4
r4(config-router)#net 4.4.4.4 0.0.0.0 area 4
r4(config-router)#end
r4#
 
r1出现了r4 的信息
 
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
     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback0
     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/2] via 192.168.3.1, 00:00:24, FastEthernet0/0
     3.0.0.0/32 is subnetted, 1 subnets
O IA    3.3.3.3 [110/3] via 192.168.3.1, 00:00:24, FastEthernet0/0
     4.0.0.0/32 is subnetted, 1 subnets
O IA    4.4.4.4 [110/4] via 192.168.3.1, 00:00:24, FastEthernet0/0
O IA 192.168.1.0/24 [110/3] via 192.168.3.1, 00:00:24, FastEthernet0/0
O IA 192.168.2.0/24 [110/2] via 192.168.3.1, 00:00:24, FastEthernet0/0
C    192.168.3.0/24 is directly connected, FastEthernet0/0
r1#
 
r4 有了路由信息
 
r4#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 IA    1.1.1.1 [110/4] via 192.168.1.2, 00:01:49, FastEthernet0/0
     2.0.0.0/32 is subnetted, 1 subnets
O IA    2.2.2.2 [110/3] via 192.168.1.2, 00:01:49, FastEthernet0/0
     3.0.0.0/32 is subnetted, 1 subnets
O IA    3.3.3.3 [110/2] via 192.168.1.2, 00:02:09, FastEthernet0/0
     4.0.0.0/32 is subnetted, 1 subnets
C       4.4.4.4 is directly connected, Loopback0
C    192.168.1.0/24 is directly connected, FastEthernet0/0
O IA 192.168.2.0/24 [110/2] via 192.168.1.2, 00:02:09, FastEthernet0/0
O IA 192.168.3.0/24 [110/3] via 192.168.1.2, 00:01:49, FastEthernet0/0
r4#
 
采用虚链路的方法，跨越的区域必须有完整的路由信息。也就是说area2 不能是末梢区域，完全末梢区域等特殊类型的区域。而且跨越的区域因为有了完整的路由信息，会增加路由器的负载。在生产环境中要特别注意防止崩溃的发生。
 
虚链路总是建立在ABR路由器之间的，至少它们之中有一个ABR路由器是必须和区域0相连的。在每一台ARB路由器的OSPF进程配置里，通过添加virtual-link命令来配置一条虚链路，并指定了这条虚链路要穿过的区域和这条链路远端的ABR的路由器ID。