1、 OSPF的NSSA区域
a、 不完全存根区域，能学习本区域连接的外部路由，能学习域间路由，不能学习其它区域的外部路由
b、 含有ASBR路由器的stub区域
c、 配置命令：area 区域号 nssa
思考：一般末节区域的路由器都是性能不是很好的，但是现在又不得不加入外网路由，没有办法，使用了NSSA区域，NSSA说白了就是不那么末节的区域，总而言之，NSSA区域就是拓扑设计的一个补救措施，本应是stub区域的，但是现在又不得以连上一个外部网络，而且是绝对NSSA区域，那么就禁止了3，4类lsa，所以就会自动推一个3类的默认路由，让去往域内的路由都匹配这个默认路由。
R1配置
en
conf t
hostname R1
int loopback 0
ip address 1.1.1.1 255.255.255.0
no shutdown
exit
int f0/0
ip address 192.168.1.1 255.255.255.0
no shutdown
exit
router ospf 1
network 1.1.1.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
exit
end
R2配置
en
conf t
hostname R2
int loopback 0
ip address 2.2.2.2 255.255.255.0
no shutdown
exit
int f0/0
ip address 192.168.1.2 255.255.255.0
no shutdown
exit
int f0/1
ip address 192.168.2.1 255.255.255.0
no shutdown
exit
router ospf 1
network 2.2.2.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
network 192.168.2.0 0.0.0.255 area 1
area 1 nssa
exit
end
R3配置
en
conf t
hostname R3
int loopback 0
ip address 3.3.3.3 255.255.255.0
no shutdown
exit
int f0/1
ip address 192.168.2.2 255.255.255.0
no shutdown
exit
int f0/0
ip address 202.168.1.1 255.255.255.0
no shutdown
exit
router ospf 1
network 192.168.2.0 0.0.0.255 area 1
network 3.3.3.0 0.0.0.255 area 1
area 1 nssa
redistribute static metric-type 1 subnets
exit
ip route 4.4.4.0 255.255.255.0 f0/0
end
R4配置
en
conf t
hostname R4
int f0/0
ip address 202.168.1.2 255.255.255.0
no shutdown
exit
int loopback 0
ip address 4.4.4.4 255.255.255.0
no shutdown
exit
ip route 0.0.0.0 0.0.0.0 f0/0
end
R2#show ip ospf database
OSPF Router with ID (2.2.2.2) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
2.2.2.2 2.2.2.2 67 0x80000004 0x00410e 2
1.1.1.1 1.1.1.1 67 0x80000003 0x00500e 2
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
192.168.1.2 2.2.2.2 67 0x80000001 0x00741f
Summary Net Link States (Area0)
Link ID ADV Router Age Seq# Checksum
192.168.2.0 2.2.2.2 47 0x80000001 0x008f5b
3.3.3.3 2.2.2.2 47 0x80000003 0x00d274
Summary ASB Link States (Area0)
Link ID ADV Router Age Seq# Checksum
2.2.2.2 2.2.2.2 2 0x8000000e 0x009b90
Router Link States (Area 1)
Link ID ADV Router Age Seq# Checksum Link count
2.2.2.2 2.2.2.2 55 0x80000002 0x005d0c 1
3.3.3.3 3.3.3.3 55 0x80000004 0x00a29d 2
Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
192.168.2.2 3.3.3.3 55 0x80000001 0x007f07
Summary Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
192.168.1.0 2.2.2.2 47 0x80000001 0x009a51
2.2.2.2 2.2.2.2 47 0x80000002 0x00f854
1.1.1.1 2.2.2.2 47 0x80000003 0x002f20
Type-7 AS External Link States(Area 1)
Link ID ADV Router Age Seq# Checksum Tag
4.4.4.0 3.3.3.3 50 0x80000001 0x000fa0 0
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
4.4.4.0 2.2.2.2 50 0x80000001 0x00dfdf 0
R2#show ip route
Codes: C – connected, S – static, I – IGRP,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 – OSPFexternal type 2, E – EGP
i – IS-IS, 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 1.1.1.1 [110/2] via 192.168.1.1, 00:01:10, FastEthernet0/0
2.0.0.0/24 is subnetted, 1 subnets
C 2.2.2.0 is directly connected, Loopback0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/2] via 192.168.2.2, 00:00:55, FastEthernet0/1
4.0.0.0/24 is subnetted, 1 subnets
O N1 4.4.4.0 [110/21] via 192.168.2.2, 00:00:55, FastEthernet0/1
C 192.168.1.0/24 is directly connected, FastEthernet0/0
C 192.168.2.0/24 is directly connected, FastEthernet0/1
解释：不完全存根区域NSSA外部路由为LSA7因为存根区域不能存在LSA5，发送到主干区域时，边界路由器转换为LSA5发送到各区域（除存根区域）。
R3#show ip ospf database
OSPF Router with ID (3.3.3.3) (Process ID 1)
Router Link States (Area 1)
Link ID ADV Router Age Seq# Checksum Link count
3.3.3.3 3.3.3.3 25 0x80000004 0x00a29d 2
2.2.2.2 2.2.2.2 25 0x80000002 0x005d0c 1
Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
192.168.2.2 3.3.3.3 25 0x80000001 0x007f07
Summary Net Link States (Area1)
Link ID ADV Router Age Seq# Checksum
192.168.1.0 2.2.2.2 17 0x80000001 0x009a51
2.2.2.2 2.2.2.2 17 0x80000002 0x00f854
1.1.1.1 2.2.2.2 17 0x80000003 0x002f20
Type-7 AS External LinkStates (Area 1)
Link ID ADV Router Age Seq# Checksum Tag
4.4.4.0 3.3.3.3 20 0x80000001 0x000fa0 0
R3#show ip route
Codes: C – connected, S – static, I – IGRP,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 – OSPFexternal type 2, E – EGP
i – IS-IS, 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 192.168.2.1, 00:01:14, FastEthernet0/1
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/2] via 192.168.2.1, 00:01:14, FastEthernet0/1
3.0.0.0/24 is subnetted, 1 subnets
C 3.3.3.0 is directly connected, Loopback0
4.0.0.0/24 is subnetted, 1 subnets
S 4.4.4.0 is directly connected, FastEthernet0/0
O IA 192.168.1.0/24 [110/2] via192.168.2.1, 00:01:14, FastEthernet0/1
C 192.168.2.0/24 is directly connected, FastEthernet0/1
C 202.168.1.0/24 is directly connected, FastEthernet0/0
解释：OIA域间路由，不完全存根区域能接受域间路由，但不接受其他区域的外部路由（本实验其他区域没有设置外部路由，只有本区域有外部路由）。