电脑知识网我们知道ospf中有几种区域类型：stub ，totally stub ,nssa ,totally nssa.
下面分别讲一下各种区域类型对路由的改变，实验图如下:
按如图配置好相关接口和参数，配置好后，查看R6路由如下：
O IA 192.168.123.0/24 [110/20] via 192.168.36.3, 00:00:04, FastEthernet0/0
1.0.0.0/32 is subnetted, 1 subnets
O IA 1.1.1.1 [110/21] via 192.168.36.3, 00:00:04, FastEthernet0/0
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/21] via 192.168.36.3, 00:00:04, FastEthernet0/0
O IA 192.168.14.0/24 [110/30] via 192.168.36.3, 00:00:04, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/11] via 192.168.36.3, 00:00:04, FastEthernet0/0
O IA 192.168.25.0/24 [110/30] via 192.168.36.3, 00:00:05, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
O IA 4.4.4.4 [110/31] via 192.168.36.3, 00:00:05, FastEthernet0/0
5.0.0.0/32 is subnetted, 1 subnets
O IA 5.5.5.5 [110/31] via 192.168.36.3, 00:00:05, FastEthernet0/0
6.0.0.0/32 is subnetted, 1 subnets
C 6.6.6.6 is directly connected, Loopback0
172.16.0.0/24 is subnetted, 4 subnets
O E2 172.16.0.0 [110/20] via 192.168.36.3, 00:00:05, FastEthernet0/0
O E2 172.16.1.0 [110/20] via 192.168.36.3, 00:00:05, FastEthernet0/0
O E2 172.16.2.0 [110/20] via 192.168.36.3, 00:00:05, FastEthernet0/0
O E2 172.16.3.0 [110/20] via 192.168.36.3, 00:00:05, FastEthernet0/0
C 192.168.36.0/24 is directly connected, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 192.168.36.3, 00:00:05, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 192.168.36.3, 00:00:05, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 192.168.36.3, 00:00:05, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 192.168.36.3, 00:00:06, FastEthernet0/0
配置R3及R6 area 3 为stub区域：
配置命令为:
R3(config-router)#area 3 stub
R6(config-router)#area 3 stub
修改完成后，R6路由如下：
O IA 192.168.123.0/24 [110/20] via 192.168.36.3, 00:00:04, FastEthernet0/0
1.0.0.0/32 is subnetted, 1 subnets
O IA 1.1.1.1 [110/21] via 192.168.36.3, 00:00:04, FastEthernet0/0
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/21] via 192.168.36.3, 00:00:04, FastEthernet0/0
O IA 192.168.14.0/24 [110/30] via 192.168.36.3, 00:00:04, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/11] via 192.168.36.3, 00:00:04, FastEthernet0/0
O IA 192.168.25.0/24 [110/30] via 192.168.36.3, 00:00:05, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
O IA 4.4.4.4 [110/31] via 192.168.36.3, 00:00:05, FastEthernet0/0
5.0.0.0/32 is subnetted, 1 subnets
O IA 5.5.5.5 [110/31] via 192.168.36.3, 00:00:05, FastEthernet0/0
6.0.0.0/32 is subnetted, 1 subnets
C 6.6.6.6 is directly connected, Loopback0
C 192.168.36.0/24 is directly connected, FastEthernet0/0
O*IA 0.0.0.0/0 [110/11] via 192.168.36.3, 00:00:07, FastEthernet0/0
由此可知stub区域不接收任何外部路由，用一条默认路由替代所有外部路由。
先在R4上查看路由表：
O IA 192.168.123.0/24 [110/20] via 192.168.14.1, 00:00:51, FastEthernet0/0
1.0.0.0/32 is subnetted, 1 subnets
O IA 1.1.1.1 [110/11] via 192.168.14.1, 00:00:51, FastEthernet0/0
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/21] via 192.168.14.1, 00:00:51, FastEthernet0/0
C 192.168.14.0/24 is directly connected, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/21] via 192.168.14.1, 00:00:51, FastEthernet0/0
O IA 192.168.25.0/24 [110/30] via 192.168.14.1, 00:00:52, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
C 4.4.4.4 is directly connected, Loopback0
5.0.0.0/32 is subnetted, 1 subnets
O IA 5.5.5.5 [110/31] via 192.168.14.1, 00:00:52, FastEthernet0/0
6.0.0.0/32 is subnetted, 1 subnets
O IA 6.6.6.6 [110/31] via 192.168.14.1, 00:00:52, FastEthernet0/0
172.16.0.0/24 is subnetted, 4 subnets
O E2 172.16.0.0 [110/20] via 192.168.14.1, 00:00:52, FastEthernet0/0
O E2 172.16.1.0 [110/20] via 192.168.14.1, 00:00:52, FastEthernet0/0
O E2 172.16.2.0 [110/20] via 192.168.14.1, 00:00:52, FastEthernet0/0
O E2 172.16.3.0 [110/20] via 192.168.14.1, 00:00:52, FastEthernet0/0
O IA 192.168.36.0/24 [110/30] via 192.168.14.1, 00:00:52, FastEthernet0/0
C 192.168.0.0/24 is directly connected, Loopback1
C 192.168.1.0/24 is directly connected, Loopback1
C 192.168.2.0/24 is directly connected, Loopback1
C 192.168.3.0/24 is directly connected, Loopback1
在R4和R1上运行以下命令：
R2(config-router)#area 2 nssa no-summary
R4(config-router)#area 2 nssa no-summary
再次查看路由表：
C 192.168.14.0/24 is directly connected, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
C 4.4.4.4 is directly connected, Loopback0
C 192.168.0.0/24 is directly connected, Loopback1
C 192.168.1.0/24 is directly connected, Loopback1
C 192.168.2.0/24 is directly connected, Loopback1
C 192.168.3.0/24 is directly connected, Loopback1
O*IA 0.0.0.0/0 [110/11] via 192.168.14.1, 00:00:19, FastEthernet0/0
由此可知nssa totally 区域去掉所区域间和外部路由
先来查看一下R5路由表：
O IA 192.168.123.0/24 [110/20] via 192.168.25.2, 00:35:59, FastEthernet0/0
1.0.0.0/32 is subnetted, 1 subnets
O IA 1.1.1.1 [110/21] via 192.168.25.2, 00:35:59, FastEthernet0/0
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/11] via 192.168.25.2, 00:35:59, FastEthernet0/0
O IA 192.168.14.0/24 [110/30] via 192.168.25.2, 00:35:59, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/21] via 192.168.25.2, 00:35:59, FastEthernet0/0
C 192.168.25.0/24 is directly connected, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
O IA 4.4.4.4 [110/31] via 192.168.25.2, 00:02:07, FastEthernet0/0
5.0.0.0/32 is subnetted, 1 subnets
C 5.5.5.5 is directly connected, Loopback0
6.0.0.0/32 is subnetted, 1 subnets
O IA 6.6.6.6 [110/31] via 192.168.25.2, 00:12:47, FastEthernet0/0
172.16.0.0/24 is subnetted, 4 subnets
C 172.16.0.0 is directly connected, Loopback1
C 172.16.1.0 is directly connected, Loopback1
C 172.16.2.0 is directly connected, Loopback1
C 172.16.3.0 is directly connected, Loopback1
O IA 192.168.36.0/24 [110/30] via 192.168.25.2, 00:12:47, FastEthernet0/0
O E2 192.168.0.0/24 [110/20] via 192.168.25.2, 00:02:02, FastEthernet0/0
O E2 192.168.1.0/24 [110/20] via 192.168.25.2, 00:02:02, FastEthernet0/0
O E2 192.168.2.0/24 [110/20] via 192.168.25.2, 00:02:02, FastEthernet0/0
O E2 192.168.3.0/24 [110/20] via 192.168.25.2, 00:02:02, FastEthernet0/0
在R2和R5上运行如下命令：
R2(config-router)#area 1 nssa
R5(config-router)#area 1 nssa
O IA 192.168.123.0/24 [110/20] via 192.168.25.2, 00:00:02, FastEthernet0/0
1.0.0.0/32 is subnetted, 1 subnets
O IA 1.1.1.1 [110/21] via 192.168.25.2, 00:00:02, FastEthernet0/0
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/11] via 192.168.25.2, 00:00:02, FastEthernet0/0
O IA 192.168.14.0/24 [110/30] via 192.168.25.2, 00:00:02, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/21] via 192.168.25.2, 00:00:02, FastEthernet0/0
C 192.168.25.0/24 is directly connected, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
O IA 4.4.4.4 [110/31] via 192.168.25.2, 00:00:03, FastEthernet0/0
5.0.0.0/32 is subnetted, 1 subnets
C 5.5.5.5 is directly connected, Loopback0
6.0.0.0/32 is subnetted, 1 subnets
O IA 6.6.6.6 [110/31] via 192.168.25.2, 00:00:03, FastEthernet0/0
172.16.0.0/24 is subnetted, 4 subnets
C 172.16.0.0 is directly connected, Loopback1
C 172.16.1.0 is directly connected, Loopback1
C 172.16.2.0 is directly connected, Loopback1
C 172.16.3.0 is directly connected, Loopback1
O IA 192.168.36.0/24 [110/30] via 192.168.25.2, 00:00:03, FastEthernet0/0
这时发现没有默认路由，需运行以下命令：
R2(config-router)#area 1 nssa default-information-originate
这时R5路由如下：
O IA 192.168.123.0/24 [110/20] via 192.168.25.2, 00:01:57, FastEthernet0/0
1.0.0.0/32 is subnetted, 1 subnets
O IA 1.1.1.1 [110/21] via 192.168.25.2, 00:01:57, FastEthernet0/0
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/11] via 192.168.25.2, 00:01:57, FastEthernet0/0
O IA 192.168.14.0/24 [110/30] via 192.168.25.2, 00:01:57, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/21] via 192.168.25.2, 00:01:57, FastEthernet0/0
C 192.168.25.0/24 is directly connected, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
O IA 4.4.4.4 [110/31] via 192.168.25.2, 00:01:59, FastEthernet0/0
5.0.0.0/32 is subnetted, 1 subnets
C 5.5.5.5 is directly connected, Loopback0
6.0.0.0/32 is subnetted, 1 subnets
O IA 6.6.6.6 [110/31] via 192.168.25.2, 00:01:59, FastEthernet0/0
172.16.0.0/24 is subnetted, 4 subnets
C 172.16.0.0 is directly connected, Loopback1
C 172.16.1.0 is directly connected, Loopback1
C 172.16.2.0 is directly connected, Loopback1
C 172.16.3.0 is directly connected, Loopback1
O IA 192.168.36.0/24 [110/30] via 192.168.25.2, 00:01:59, FastEthernet0/0
O*N2 0.0.0.0/0 [110/1] via 192.168.25.2, 00:00:06, FastEthernet0/0