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拓扑图如下：将Area2作为Stub&Totally Stub



1、Stub区域
R1的路由配置
r1(config)#router ospf 100
r1(config-router)#router-id 1.1.1.1
r1(config-router)#net 1.1.12.1 0.0.0.0 a 1
r1(config)#router rip
r1(config-router)#ver 2
r1(config-router)#no auto-summary
r1(config-router)#net 11.0.0.0
r1(config-router)#exit

R2的路由配置

r2(config)#router ospf 100
r2(config-router)#router
r2(config-router)#router-id 2.2.2.2
r2(config-router)#net 1.1.12.2 0.0.0.0 a 1
r2(config-router)#net 1.1.23.2 0.0.0.0 a 0
r2(config-router)#net 2.2.2.2 0.0.0.0 a 0
r2(config-router)#

r3(config)#router ospf 100
r3(config-router)#router
r3(config-router)#router-id 3.3.3.3
r3(config-router)#net 3.3.3.3 0.0.0.0 a 2
r3(config-router)#net 1.1.23.3 0.0.0.0 a 0
r3(config-router)#net 1.1.34.3 0.0.0.0 a 2

路由配置完后，我们现在要构造出类型5的LSA，这样才能使得实验效果明显，我们在R1上配置两个路由协议，现在把R1做成ASBR将RIP协议在发布到OSPF中，这样R1就会产生类型5的LSA向下传递，我们把区域2做成stub区域，做成后类型5的路由会拒绝接收，现在来看看具体做法：


（1）  首先完成RIP到OSPF的再发布
r1(config)#router ospf 100
r1(config-router)#redistribute rip subnets
（2）  看一下现在R4的路由表
r4#sho ip route ospf
     1.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O IA    1.1.1.1/32 [110/2344] via 1.1.34.3, 00:00:49, Serial0/0/1
O IA    1.1.12.0/24 [110/2343] via 1.1.34.3, 00:05:35, Serial0/0/1
O IA    1.1.23.0/24 [110/1562] via 1.1.34.3, 00:05:35, Serial0/0/1
     2.0.0.0/32 is subnetted, 1 subnets
O IA    2.2.2.2 [110/1563] via 1.1.34.3, 00:05:35, Serial0/0/1
     3.0.0.0/32 is subnetted, 1 subnets
O       3.3.3.3 [110/782] via 1.1.34.3, 00:05:35, Serial0/0/1
     11.0.0.0/24 is subnetted, 1 subnets
O E2    11.11.11.0 [110/20] via 1.1.34.3, 00:00:21, Serial0/0/1
会发现除了O  OIA的路由还多了一条OE2的路由，这个路由就是外部路由，我们来看一下R4的LSDB
r4#show ip os database

            OSPF Router with ID (4.4.4.4) (Process ID 100)

                Router Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum Link count
3.3.3.3         3.3.3.3         392         0x80000004 0x00F1AA 2
4.4.4.4         4.4.4.4         391         0x80000001 0x003282 1

                Net Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum
1.1.34.3        3.3.3.3         392         0x80000001 0x00C525

                Summary Net Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum
1.1.1.1         3.3.3.3         102         0x80000001 0x0046C5
1.1.12.0        3.3.3.3         471         0x80000001 0x00CC36
1.1.23.0        3.3.3.3         471         0x80000001 0x00B552
2.2.2.2         3.3.3.3         471         0x80000001 0x007A9D

                Summary ASB Link States (Area 2) 类型4的LSA， 通告ASBR的RID
          
Link ID         ADV Router      Age         Seq#       Checksum
1.1.1.1         3.3.3.3         227         0x80000001 0x002EDD

                Type-5 AS External Link States 类型5的LSA，通告ASBR的外部网络

Link ID         ADV Router      Age         Seq#       Checksum Tag
11.11.11.0      1.1.1.1         79          0x80000001 0x003C3F 0
r4#

我们发现R4的LSDB中多了类型4和类型5的LSA
（3）现在我们把区域2做成Stub区域
r3(config)#
r3(config)#router ospf 100
r3(config-router)#area 2 stub
r3(config-router)#

r4(config)#router ospf 100
r4(config-router)#area 2 stub
r4(config-router)#

然后我们来看看R4的路由表
r4#show ip route ospf
     1.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O IA    1.1.1.1/32 [110/2344] via 1.1.34.3, 00:00:46, Serial0/0/1
O IA    1.1.12.0/24 [110/2343] via 1.1.34.3, 00:00:46, Serial0/0/1
O IA    1.1.23.0/24 [110/1562] via 1.1.34.3, 00:00:46, Serial0/0/1
     2.0.0.0/32 is subnetted, 1 subnets
O IA    2.2.2.2 [110/1563] via 1.1.34.3, 00:00:46, Serial0/0/1
     3.0.0.0/32 is subnetted, 1 subnets
O       3.3.3.3 [110/782] via 1.1.34.3, 00:00:46, Serial0/0/1
O*IA 0.0.0.0/0 [110/782] via 1.1.34.3, 00:00:46, Serial0/0/1
r4#
我们发现此时R4的路由表中没有了OE2的路由，而只有O 和OIA还有一条O*IA的路由，O*IA的路由是由R3向R4区域注入的，我们再看看R4的LSDB的变化
r4#show ip os da

            OSPF Router with ID (4.4.4.4) (Process ID 100)

                Router Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum Link count
3.3.3.3         3.3.3.3         197         0x80000006 0x001685 2
4.4.4.4         4.4.4.4         196         0x80000003 0x00565D 1

                Net Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum
1.1.34.4        4.4.4.4         195         0x80000001 0x00AB3C

                Summary Net Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum
0.0.0.0         3.3.3.3         211         0x80000001 0x0057DA
1.1.1.1         3.3.3.3         211         0x80000002 0x0062AA
1.1.12.0        3.3.3.3         211         0x80000002 0x00E81B
1.1.23.0        3.3.3.3         211         0x80000002 0x00D137
2.2.2.2         3.3.3.3         211         0x80000002 0x009682
r4#
我们发现类型4和类型5的LSA已经没有了，只有 类型一 二和三的LSA
我们用show ip ospf来看看R4的OSPF的基本情况
r4#show ip os
Routing Process "ospf 100" with ID 4.4.4.4
Start time: 03:03:03.900, Time elapsed: 00:15:10.104
Supports only single TOS(TOS0) routes
……..
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 1. 0 normal 1 stub 0 nssa
Number of areas transit capable is 0
External flood list length 0
我们发现该路由有1个stub！
最后测试一下R4与外界的连通性：
r4#ping 11.11.11.11

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 11.11.11.11, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 168/168/168 ms
r4#
测试成功，网络OK！