搭建实验环境：
实现此案例需要按照如下步骤进行。
interface GigabitEthernet0/0/1
ip address 192.168.12.1 255.255.255.0
interface GigabitEthernet0/0/0
ip address 192.168.13.1 255.255.255.0
ospf 1 router-id 1.1.1.1
import-route static cost 100 type 2
area 0.0.0.1
network 192.168.12.0 0.0.0.255
nssa
ip route-static 192.168.3.0 255.255.255.0 192.168.13.3
interface GigabitEthernet0/0/0
ip address 192.168.24.2 255.255.255.0
interface GigabitEthernet0/0/1
ip address 192.168.12.2 255.255.255.0
ospf 1 router-id 2.2.2.2
area 0.0.0.0
network 192.168.24.0 0.0.0.255
area 0.0.0.1
network 192.168.12.0 0.0.0.255
nssa
interface GigabitEthernet0/0/0
ip address 192.168.13.3 255.255.255.0
interface LoopBack0
ip address 192.168.3.3 255.255.255.0
ip route-static 0.0.0.0 0.0.0.0 192.168.13.1
interface GigabitEthernet0/0/0
ip address 192.168.24.4 255.255.255.0
ospf 1 router-id 4.4.4.4
area 0.0.0.0
network 192.168.24.0 0.0.0.255
<R1>dis ip ro
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 13 Routes : 13
Destination/Mask Proto Pre Cost Flags NextHop Interface
0.0.0.0/0 O_NSSA 150 1 D 192.168.12.2 GigabitEthernet
0/0/1
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
192.168.3.0/24 Static 60 0 RD 192.168.13.3 GigabitEthernet
0/0/0
192.168.12.0/24 Direct 0 0 D 192.168.12.1 GigabitEthernet
0/0/1
192.168.12.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
192.168.12.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
192.168.13.0/24 Direct 0 0 D 192.168.13.1 GigabitEthernet
0/0/0
192.168.13.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
192.168.13.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
192.168.24.0/24 OSPF 10 2 D 192.168.12.2 GigabitEthernet
0/0/1
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
<R1>dis ospf ro
OSPF Process 1 with Router ID 1.1.1.1
Routing Tables
Routing for Network
Destination Cost Type NextHop AdvRouter Area
192.168.12.0/24 1 Transit 192.168.12.1 1.1.1.1 0.0.0.1
192.168.24.0/24 2 Inter-area 192.168.12.2 2.2.2.2 0.0.0.1
Routing for NSSAs
Destination Cost Type Tag NextHop AdvRouter
0.0.0.0/0 1 Type2 1 192.168.12.2 2.2.2.2
Total Nets: 3
Intra Area: 1 Inter Area: 1 ASE: 0 NSSA: 1
<R2>dis ip ro
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 11 Routes : 11
Destination/Mask Proto Pre Cost Flags NextHop Interface
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
192.168.3.0/24 O_NSSA 150 100 D 192.168.12.1 GigabitEthernet
0/0/1
192.168.12.0/24 Direct 0 0 D 192.168.12.2 GigabitEthernet
0/0/1
192.168.12.2/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
192.168.12.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
192.168.24.0/24 Direct 0 0 D 192.168.24.2 GigabitEthernet
0/0/0
192.168.24.2/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
192.168.24.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
<R2>dis ospf ro
OSPF Process 1 with Router ID 2.2.2.2
Routing Tables
Routing for Network
Destination Cost Type NextHop AdvRouter Area
192.168.12.0/24 1 Transit 192.168.12.2 2.2.2.2 0.0.0.1
192.168.24.0/24 1 Transit 192.168.24.2 2.2.2.2 0.0.0.0
Routing for NSSAs
Destination Cost Type Tag NextHop AdvRouter
192.168.3.0/24 100 Type2 1 192.168.12.1 1.1.1.1
Total Nets: 3
Intra Area: 2 Inter Area: 0 ASE: 0 NSSA: 1
<R3>dis ip ro
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 11 Routes : 11
Destination/Mask Proto Pre Cost Flags NextHop Interface
0.0.0.0/0 Static 60 0 RD 192.168.13.1 GigabitEthernet
0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
192.168.3.0/24 Direct 0 0 D 192.168.3.3 LoopBack0
192.168.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
192.168.3.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
192.168.13.0/24 Direct 0 0 D 192.168.13.3 GigabitEthernet
0/0/0
192.168.13.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
192.168.13.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
<R4>dis ip ro
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 9 Routes : 9
Destination/Mask Proto Pre Cost Flags NextHop Interface
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
192.168.3.0/24 O_ASE 150 100 D 192.168.24.2 GigabitEthernet
0/0/0
192.168.12.0/24 OSPF 10 2 D 192.168.24.2 GigabitEthernet
0/0/0
192.168.24.0/24 Direct 0 0 D 192.168.24.4 GigabitEthernet
0/0/0
192.168.24.4/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
192.168.24.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
<R4>dis ospf ro
OSPF Process 1 with Router ID 4.4.4.4
Routing Tables
Routing for Network
Destination Cost Type NextHop AdvRouter Area
192.168.24.0/24 1 Transit 192.168.24.4 4.4.4.4 0.0.0.0
192.168.12.0/24 2 Inter-area 192.168.24.2 2.2.2.2 0.0.0.0
Routing for ASEs
Destination Cost Type Tag NextHop AdvRouter
192.168.3.0/24 100 Type2 1 192.168.24.2 2.2.2.2
Total Nets: 3
Intra Area: 1 Inter Area: 1 ASE: 1 NSSA: 0
