拓扑如图↓

配好ip/协议后,各设备路由如图↓

FW1
H>* 1.1.1.1/32 [0/0/1] is local address, loopback1
C>* 10.1.1.0/30 is directly connected, ethernet0/1
H>* 10.1.1.1/32 [0/0/1] is local address, ethernet0/1
C>* 20.1.1.0/30 is directly connected, ethernet0/2
H>* 20.1.1.1/32 [0/0/1] is local address, ethernet0/2
C>* 192.168.1.0/24 is directly connected, ethernet0/0
H>* 192.168.1.1/32 [0/0/1] is local address, ethernet0/0

RT1
C 10.1.1.0/30 is directly connected, GigaEthernet0/5
R 20.1.1.0/30 [120,1] via 10.1.1.1(on GigaEthernet0/5)
C 30.1.1.0/30 is directly connected, GigaEthernet0/4
O 40.1.1.0/30 [110,2] via 50.1.1.2(on GigaEthernet0/3)
              [110,2] via 30.1.1.2(on GigaEthernet0/4)
C 50.1.1.0/30 is directly connected, GigaEthernet0/3
R 192.168.1.0/24 [120,1] via 10.1.1.1(on GigaEthernet0/5)

RT2
R 10.1.1.0/30 [120,1] via 20.1.1.1(on GigaEthernet0/5)
C 20.1.1.0/30 is directly connected, GigaEthernet0/5
O 30.1.1.0/30 [110,2] via 50.1.1.1(on GigaEthernet0/3)
              [110,2] via 40.1.1.2(on GigaEthernet0/4)
C 40.1.1.0/30 is directly connected, GigaEthernet0/4
C 50.1.1.0/30 is directly connected, GigaEthernet0/3
R 192.168.1.0/24 [120,1] via 20.1.1.1(on GigaEthernet0/5)

RT3
C 30.1.1.0/30 is directly connected, GigaEthernet0/4
C 40.1.1.0/30 is directly connected, GigaEthernet0/3
O 50.1.1.0/30 [110,2] via 40.1.1.1(on GigaEthernet0/3)
              [110,2] via 30.1.1.1(on GigaEthernet0/4)

在RT1上和RT2上双向路由引入,查看路由表

RT1
C 10.1.1.0/30 is directly connected, GigaEthernet0/5
R 20.1.1.0/30 [120,1] via 10.1.1.1(on GigaEthernet0/5)
C 30.1.1.0/30 is directly connected, GigaEthernet0/4
O 40.1.1.0/30 [110,2] via 50.1.1.2(on GigaEthernet0/3)
              [110,2] via 30.1.1.2(on GigaEthernet0/4)
C 50.1.1.0/30 is directly connected, GigaEthernet0/3
R 192.168.1.0/24 [120,1] via 10.1.1.1(on GigaEthernet0/5)

RT2
R 10.1.1.0/30 [120,1] via 20.1.1.1(on GigaEthernet0/5)
C 20.1.1.0/30 is directly connected, GigaEthernet0/5
O 30.1.1.0/30 [110,2] via 50.1.1.1(on GigaEthernet0/3)
              [110,2] via 40.1.1.2(on GigaEthernet0/4)
C 40.1.1.0/30 is directly connected, GigaEthernet0/4
C 50.1.1.0/30 is directly connected, GigaEthernet0/3
R 192.168.1.0/24 [120,1] via 20.1.1.1(on GigaEthernet0/5)

查看RT1和RT2的LSDB表

RT1
                          AREA: 0
                   Router Link States 
Link ID         ADV Router      Age        Seq Num    Checksum Link Count 
1.1.1.1         1.1.1.1         332        0x80000008 0x6df9   2    
2.2.2.2         2.2.2.2         319        0x80000008 0xd475   2    
3.3.3.3         3.3.3.3         1120       0x80000005 0x3935   2    
                   Net Link States 
Link ID         ADV Router      Age        Seq Num    Checksum 
40.1.1.1        2.2.2.2         1160       0x80000003 0x1bda   
30.1.1.1        1.1.1.1         1289       0x80000003 0x996e   
50.1.1.1        1.1.1.1         1289       0x80000003 0x6295   


                  ASE Link States 
Link ID         ADV Router      Age        Seq Num    Checksum  Tag     
20.1.1.0        1.1.1.1         331        0x80000001 0xbe7a    0x00000000
192.168.1.0     2.2.2.2         322        0x80000001 0x12cb    0x00000000 
192.168.1.0     1.1.1.1         331        0x80000001 0x30b1    0x00000000
10.1.1.0        2.2.2.2         327        0x80000001 0x231c    0x00000000

RT2                   

                          AREA: 0
                   Router Link States 
Link ID         ADV Router      Age        Seq Num    Checksum Link Count 
2.2.2.2         2.2.2.2         430        0x80000008 0xd475   2    
1.1.1.1         1.1.1.1         445        0x80000008 0x6df9   2    
3.3.3.3         3.3.3.3         1231       0x80000005 0x3935   2    
                   Net Link States 
Link ID         ADV Router      Age        Seq Num    Checksum 
30.1.1.1        1.1.1.1         1402       0x80000003 0x996e   
40.1.1.1        2.2.2.2         1270       0x80000003 0x1bda   
50.1.1.1        1.1.1.1         1402       0x80000003 0x6295   


                  ASE Link States 
Link ID         ADV Router      Age        Seq Num    Checksum 
10.1.1.0        2.2.2.2         438        0x80000001 0x231c  
192.168.1.0     2.2.2.2         433        0x80000001 0x12cb  
192.168.1.0     1.1.1.1         444        0x80000001 0x30b1  
20.1.1.0        1.1.1.1         444        0x80000001 0xbe7a  

此时可以发现RT1/RT2通过路由引入将192.168.1.0/24这条路由信息传给了RT2/RT1,因为ospf路由引入的优先级为150,所以会选择通过RIP协议传过来的路由信息,RIP优先级为120。此时的拓扑没有环路。

再加上一台运行了ospf的设备↓

做好ospf后,把LSW1的L0引入到ospf内

查看RT1,FW1,RT2的路由表↓

RT1
R 1.1.1.1/32 [120,2] via 10.1.1.1(on GigaEthernet0/5)
C 10.1.1.0/30 is directly connected, GigaEthernet0/5
R 20.1.1.0/30 [120,1] via 10.1.1.1(on GigaEthernet0/5)
C 30.1.1.0/30 is directly connected, GigaEthernet0/4
O 40.1.1.0/30 [110,2] via 50.1.1.2(on GigaEthernet0/3)
              [110,2] via 30.1.1.2(on GigaEthernet0/4)
C 50.1.1.0/30 is directly connected, GigaEthernet0/3
O 60.1.1.0/30 [110,2] via 50.1.1.2(on GigaEthernet0/3)
R 192.168.1.0/24 [120,1] via 10.1.1.1(on GigaEthernet0/5)

FW1
R>* 1.1.1.1/32 [120/2/1] via 20.1.1.2, ethernet0/2, 00:02:09
C>* 10.1.1.0/30 is directly connected, ethernet0/1
H>* 10.1.1.1/32 [0/0/1] is local address, ethernet0/1
C>* 20.1.1.0/30 is directly connected, ethernet0/2
H>* 20.1.1.1/32 [0/0/1] is local address, ethernet0/2
R>* 30.1.1.0/30 [120/2/1] via 20.1.1.2, ethernet0/2, 00:26:54
R>* 40.1.1.0/30 [120/2/1] via 10.1.1.2, ethernet0/1, 00:27:21
R>* 60.1.1.0/30 [120/2/1] via 10.1.1.2, ethernet0/1, 00:05:20
C>* 192.168.1.0/24 is directly connected, ethernet0/0
H>* 192.168.1.1/32 [0/0/1] is local address, ethernet0/0

RT2
R 1.1.1.1/32 [120,2] via 20.1.1.1(on GigaEthernet0/5)
R 10.1.1.0/30 [120,1] via 20.1.1.1(on GigaEthernet0/5)
C 20.1.1.0/30 is directly connected, GigaEthernet0/5
O 30.1.1.0/30 [110,2] via 50.1.1.1(on GigaEthernet0/3)
               [110,2] via 40.1.1.2(on GigaEthernet0/4)
C 40.1.1.0/30 is directly connected, GigaEthernet0/4
C 50.1.1.0/30 is directly connected, GigaEthernet0/3
C 60.1.1.0/30 is directly connected, GigaEthernet0/6
R 192.168.1.0/24 [120,1] via 20.1.1.1(on GigaEthernet0/5)

此时可以发现环路了。因为LSW1把路由传给RT2(优先级150),RT2传给RT1(优先级150)、FW1(通过路由引入,优先级为120),RT1传给FW1(优先级120),FW1传给RT2(优先级为120),所以RT2去往1.1.1.1下一跳为FW1。

解决方法↓

  • 在RT2上修改ospf外部路由优先级使外部路由优先级为x(x<120)

router ospf 1
distance ospf external 100
  • 在RT2上使用ACL/Prefix-list 匹配1.1.1.1/32路由,在rip视图下使用过滤工具进行过滤

ip prefix-list 1 seq 10 deny 1.1.1.1/32
ip prefix-list 1 seq 20 permit any
---------------------or---------------------
ip access-list standard 1
 deny 1.1.1.1 255.255.255.255
 permit any 

router rip 
filter gigaEthernet 0/5 in access-list/prefix-list 1

 


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