OSPF的LSA有11类，常用的也就是1（路由器本身）、3（网络汇总）、5类（AS外部路由）；

7类LSA（是非完全末梢区域下才会产生7类LSA）

NSSA（not-so-stubby area）是由NSSA区域内的 ASBR 路由器始发的 LSA 通告它只在 NSSA 区域内泛洪；和5类LSA区别就是传播的范围(5类是在整个AS区域中泛洪，7类只能在NSSA区域中泛洪)

如下图的网络拓扑（不能插入图片真麻烦）：

外部---R1---R2---R3---R4----R5---R6

R1/R2在Area 2

R2/R3在Area 0

R3/R4/R5 在Area 1 为NSSA区域

R5/R6模拟的外部网络。

NSSA区域的配置：

R3的配置信息：

router ospf 1
 log-adjacency-changes
 area 1 nssa
 redistribute connected subnets
 network 192.168.2.0 0.0.0.255 area 0
 network 192.168.3.0 0.0.0.255 area 1
!

如果在其他非NSSA区域的边界路由器上存在外部路由的注入，如RIP的路由注入；

在R1上配置

router ospf 1
 log-adjacency-changes
 redistribute rip metric 1 subnets
 network 1.1.1.0 0.0.0.255 area 2
 network 192.168.1.0 0.0.0.255 area 2
!
router rip
 version 2
 redistribute ospf 1 metric 1
 network 10.0.0.0
 no auto-summary
!

查看路由信息：

R3的路由查看

R3#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 [110/3] via 192.168.2.2, 01:43:05, FastEthernet0/1
     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/2] via 192.168.2.2, 01:43:10, FastEthernet0/1
     3.0.0.0/24 is subnetted, 1 subnets
C       3.3.3.0 is directly connected, Loopback3
     4.0.0.0/32 is subnetted, 1 subnets
O       4.4.4.4 [110/11] via 192.168.3.4, 01:43:05, Ethernet1/1
     5.0.0.0/32 is subnetted, 1 subnets
O       5.5.5.5 [110/21] via 192.168.3.4, 01:43:05, Ethernet1/1
O    192.168.4.0/24 [110/20] via 192.168.3.4, 01:43:05, Ethernet1/1
O N2 192.168.5.0/24 [110/20] via 192.168.3.4, 01:42:58, Ethernet1/1
     10.0.0.0/24 is subnetted, 1 subnets
O E2    10.1.1.0 [110/1] via 192.168.2.2, 01:43:06, FastEthernet0/1
O IA 192.168.1.0/24 [110/2] via 192.168.2.2, 01:43:06, FastEthernet0/1
C    192.168.2.0/24 is directly connected, FastEthernet0/1
C    192.168.3.0/24 is directly connected, Ethernet1/1

R4的路由信息：
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 [110/13] via 192.168.3.3, 01:43:40, Ethernet1/1
     2.0.0.0/32 is subnetted, 1 subnets
O IA    2.2.2.2 [110/12] via 192.168.3.3, 01:43:40, Ethernet1/1
     3.0.0.0/24 is subnetted, 1 subnets
O N2    3.3.3.0 [110/20] via 192.168.3.3, 01:43:40, Ethernet1/1
     4.0.0.0/24 is subnetted, 1 subnets
C       4.4.4.0 is directly connected, Loopback4
     5.0.0.0/32 is subnetted, 1 subnets
O       5.5.5.5 [110/11] via 192.168.4.5, 01:43:40, Ethernet1/0
C    192.168.4.0/24 is directly connected, Ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 01:43:40, Ethernet1/0
O IA 192.168.1.0/24 [110/12] via 192.168.3.3, 01:43:40, Ethernet1/1
O IA 192.168.2.0/24 [110/11] via 192.168.3.3, 01:43:41, Ethernet1/1
C    192.168.3.0/24 is directly connected, Ethernet1/1
配置完NSSA属性之后，就会产生相应的域间路由信息；如果再引入外部路由的情况下，需要在nssa区域的ABR上注入默认的路由保证，NSSA区域的能够正常访问外部网络。否则就会出现网络无法访问的情况；

命令如下：

area 1 nssa default-information-originate

在R4上的路由信息：
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 192.168.3.3 to network 0.0.0.0
     1.0.0.0/32 is subnetted, 1 subnets
O IA    1.1.1.1 [110/13] via 192.168.3.3, 01:55:07, Ethernet1/1
     2.0.0.0/32 is subnetted, 1 subnets
O IA    2.2.2.2 [110/12] via 192.168.3.3, 01:55:07, Ethernet1/1
     3.0.0.0/24 is subnetted, 1 subnets
O N2    3.3.3.0 [110/20] via 192.168.3.3, 01:55:07, Ethernet1/1
     4.0.0.0/24 is subnetted, 1 subnets
C       4.4.4.0 is directly connected, Loopback4
     5.0.0.0/32 is subnetted, 1 subnets
O       5.5.5.5 [110/11] via 192.168.4.5, 01:55:07, Ethernet1/0
C    192.168.4.0/24 is directly connected, Ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 01:55:07, Ethernet1/0
O IA 192.168.1.0/24 [110/12] via 192.168.3.3, 01:55:07, Ethernet1/1
O IA 192.168.2.0/24 [110/11] via 192.168.3.3, 01:55:07, Ethernet1/1
C    192.168.3.0/24 is directly connected, Ethernet1/1
O*N2 0.0.0.0/0 [110/1] via 192.168.3.3, 00:00:36, Ethernet1/1
NSSA区域的路由起上就会产生一条7类的默认路由，在整个NSSA区域泛洪；同时又有一些域间的路由和默认路由，这样为了减少路由的条目数就对路由进行简化，因此产生完全末梢区域对路由进行精简

命令：area 1 nssa no-summary

完全末梢区域会自动产生一条3类LSA的默认路由并在整个NSSA区域中泛洪：
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 192.168.3.3 to network 0.0.0.0
     3.0.0.0/24 is subnetted, 1 subnets
O N2    3.3.3.0 [110/20] via 192.168.3.3, 00:00:17, Ethernet1/1
     4.0.0.0/24 is subnetted, 1 subnets
C       4.4.4.0 is directly connected, Loopback4
     5.0.0.0/32 is subnetted, 1 subnets
O       5.5.5.5 [110/11] via 192.168.4.5, 00:00:17, Ethernet1/0
C    192.168.4.0/24 is directly connected, Ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 00:00:17, Ethernet1/0
C    192.168.3.0/24 is directly connected, Ethernet1/1
O*IA 0.0.0.0/0 [110/11] via 192.168.3.3, 00:00:17, Ethernet1/1

查看数据库信息：
                Summary Net Link States (Area 1)

Link ID         ADV Router      Age         Seq#       Checksum
0.0.0.0         3.3.3.3         137         0x80000001 0x00DE4B

注意：配置完全末梢区域的时候，只需要在NSSA的ABR上配置就可以，其他的NSSA路由器上正常配置就可以。

如果在NSSA区域和骨干区域的路由上引入外部路由如在R3上引入外部路由，

在R4上查看的路由信息：

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 192.168.3.3 to network 0.0.0.0
     3.0.0.0/24 is subnetted, 1 subnets
O N2    3.3.3.0 [110/20] via 192.168.3.3, 00:00:17, Ethernet1/1
     4.0.0.0/24 is subnetted, 1 subnets
C       4.4.4.0 is directly connected, Loopback4
     5.0.0.0/32 is subnetted, 1 subnets
O       5.5.5.5 [110/11] via 192.168.4.5, 00:00:17, Ethernet1/0
C    192.168.4.0/24 is directly connected, Ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 00:00:17, Ethernet1/0
C    192.168.3.0/24 is directly connected, Ethernet1/1
O*IA 0.0.0.0/0 [110/11] via 192.168.3.3, 00:00:17, Ethernet1/1

如果设备存在大量的引入的路由信息，这样也会对设备的CPU消耗比较大，为简化路由引入另外一条命令：area 1 nssa no-summary no-redistribution

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 192.168.3.3 to network 0.0.0.0
     4.0.0.0/24 is subnetted, 1 subnets
C       4.4.4.0 is directly connected, Loopback4
     5.0.0.0/32 is subnetted, 1 subnets
O       5.5.5.5 [110/11] via 192.168.4.5, 00:00:03, Ethernet1/0
C    192.168.4.0/24 is directly connected, Ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 00:00:03, Ethernet1/0
C    192.168.3.0/24 is directly connected, Ethernet1/1
O*IA 0.0.0.0/0 [110/11] via 192.168.3.3, 00:00:03, Ethernet1/1
一般情况下，配置NSSA区域的时候，在ABR上配置no-summary 和no-redistribution结合使用。但不要搞混淆了，只在NSSA区域的ABR路由上配置，其他的NSSA路由器上只配置为NSSA区域就行。

NSSA区域 default-information-originate/no-redistribution/ no-summary区别