【实验拓扑】
【实验基本配置】
1、按照上图配置相应接口以及OSPF
【实验要求】
1、配置Area 1 为NSSA区域
2、在R6上配置1条静态路由
160.1.60.0/24指向 Null0，并充分发到OSPF中
3、将路由器1的ID修改为
150.1.100.100
【实验分析】
- 次末节区域（NSSA）定义：不接受本自治域系统（OSPF网络）之外的路由，但是他允许引入类型7的LSA的外部路由，并将特定的类型7的LSA路由转换为来威胁5的LSA。
- 什么情况下使用次末节区域：例如下图中，区域1中的路由器没有足够的性能处理OSPF时，该怎么办？我们可以把区域1配置为末节区域或次末节区域，来减少OSPF路由器的负担，但这样会出现1个问题，RIP将无法通告到OSPF中。此时利用次末节区域能够很好的解决这一问题。
- 配置次末节区域时注意事项，必须在该区域中的所有路由器上进行配置，否则该区域中的路由器将无法达到毗邻状态。
【实验配置】
R1,R4,R6:
router ospf 1
area 1 nssa
R6:
ip route 160.1.60.0 255.255.255.0 Null0
router ospf 1
redistribute static subnets
R1:
router ospf 1
router-id 150.1.100.100
【实验验证】
配置之前--------------------------------------------------------->>
R1#show ip route ospf
160.1.0.0/24 is subnetted, 1 subnets
O E2 160.1.60.0 [110/20] via 155.1.146.6, 00:00:41, FastEthernet0/0
150.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
O 150.1.6.6/32 [110/2] via 155.1.146.6, 00:00:41, FastEthernet0/0
O 150.1.5.5/32 [110/65] via 155.1.0.5, 00:01:24, Serial0/0
O 150.1.4.4/32 [110/2] via 155.1.146.4, 00:00:41, FastEthernet0/0
R4#show ip route ospf
160.1.0.0/24 is subnetted, 1 subnets
O N2 160.1.60.0 [110/20] via 155.1.146.6, 00:01:10, Ethernet0/1
150.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
O 150.1.6.6/32 [110/11] via 155.1.146.6, 00:01:10, Ethernet0/1
O 150.1.5.5/32 [110/391] via 155.1.0.5, 00:01:25, Serial0/0
O 150.1.1.1/32 [110/11] via 155.1.146.1, 00:01:10, Ethernet0/1
R5#show ip route ospf
155.1.0.0/24 is subnetted, 3 subnets
O IA 155.1.146.0 [110/391] via 155.1.0.1, 00:01:28, Serial0/0
160.1.0.0/24 is subnetted, 1 subnets
O E2 160.1.60.0 [110/20] via 155.1.0.1, 00:02:06, Serial0/0
150.1.0.0/16 is variably subnetted, 5 subnets, 2 masks
O IA 150.1.6.6/32 [110/392] via 155.1.0.1, 00:01:42, Serial0/0
O IA 150.1.4.4/32 [110/391] via 155.1.0.4, 00:04:42, Serial0/0
O IA 150.1.1.1/32 [110/391] via 155.1.0.1, 00:04:36, Serial0/0
R5#show ip ospf database external 160.1.60.0
OSPF Router with ID (150.1.5.5) (Process ID 1)
Type-5 AS External Link States
Routing Bit Set on this LSA
LS age: 226
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 160.1.60.0 (External Network Number )
Advertising Router: 150.1.4.4
LS Seq Number: 80000001
Checksum: 0xBCC2
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 150.1.6.6
External Route Tag: 0
R1#show ip ospf database external 160.1.60.0
OSPF Router with ID (150.1.1.1) (Process ID 1)
Type-5 AS External Link States
Routing Bit Set on this LSA
LS age: 321
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 160.1.60.0 (External Network Number )
Advertising Router: 150.1.4.4
LS Seq Number: 80000001
Checksum: 0xBCC2
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 150.1.6.6
External Route Tag: 0
R4#show ip ospf database nssa-external 160.1.60.0
OSPF Router with ID (150.1.4.4) (Process ID 1)
Type-7 AS External Link States (Area 1)
Routing Bit Set on this LSA
LS age: 376
Options: (No TOS-capability, Type 7/5 translation, DC)
LS Type: AS External Link
Link State ID: 160.1.60.0 (External Network Number )
Advertising Router: 150.1.6.6
LS Seq Number: 80000001
Checksum: 0xE63
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 150.1.6.6
External Route Tag: 0
配置之后------------------------------------------------>>
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#router ospf 1
R1(config-router)#router-id 150.1.100.100
Reload or use "clear ip ospf process" command, for this to take effect
R1(config-router)#^Z
R1#clear ip ospf process
Reset ALL OSPF processes? [no]: yes
R1#show ip route ospf
160.1.0.0/24 is subnetted, 1 subnets
O N2 160.1.60.0 [110/20] via 155.1.146.6, 00:00:01, FastEthernet0/0
150.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
O 150.1.6.6/32 [110/2] via 155.1.146.6, 00:00:30, FastEthernet0/0
O 150.1.5.5/32 [110/65] via 155.1.0.5, 00:00:01, Serial0/0
O 150.1.4.4/32 [110/2] via 155.1.146.4, 00:00:30, FastEthernet0/0
R4#show ip route ospf
160.1.0.0/24 is subnetted, 1 subnets
O E2 160.1.60.0 [110/20] via 155.1.146.6, 00:00:08, Ethernet0/1
150.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
O 150.1.6.6/32 [110/11] via 155.1.146.6, 00:00:27, Ethernet0/1
O 150.1.5.5/32 [110/391] via 155.1.0.5, 00:00:08, Serial0/0
O 150.1.1.1/32 [110/11] via 155.1.146.1, 00:00:27, Ethernet0/1
R5#show ip route ospf
155.1.0.0/24 is subnetted, 3 subnets
O IA 155.1.146.0 [110/391] via 155.1.0.1, 00:00:17, Serial0/0
160.1.0.0/24 is subnetted, 1 subnets
O E2 160.1.60.0 [110/20] via 155.1.0.1, 00:00:17, Serial0/0
150.1.0.0/16 is variably subnetted, 5 subnets, 2 masks
O IA 150.1.6.6/32 [110/392] via 155.1.0.1, 00:00:17, Serial0/0
O IA 150.1.4.4/32 [110/391] via 155.1.0.4, 00:00:17, Serial0/0
O IA 150.1.1.1/32 [110/391] via 155.1.0.1, 00:00:17, Serial0/0
R5#show ip ospf database external 160.1.60.0
OSPF Router with ID (150.1.5.5) (Process ID 1)
Type-5 AS External Link States
Routing Bit Set on this LSA
LS age: 45
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 160.1.60.0 (External Network Number )
Advertising Router: 150.1.100.100
LS Seq Number: 80000001
Checksum: 0xD7E6
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 150.1.6.6
External Route Tag: 0
本文转自zcm8483 51CTO博客，原文链接:http://blog.51cto.com/haolun/993178
