我們知道ospf中有幾種區域類型：stub ，totally stub ,nssa ,totally nssa.

　　下面分別講一下各種區域類型對路由的改變，實驗圖如下:

　　按如圖配置好相關接口和參數，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 為stub區域：

　　配置命令為:

　　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區域不接收任何外部路由，用一條默認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上運行以下命令：

　　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 區域去掉所區域間和外部路由

　先來查看一下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上運行如下命令：

　　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

　　這時發現沒有默認路由，需運行以下命令：

　　R2(config-router)#area 1 nssa default-information-originate

　　這時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