OSPF邻居认证实际案例及验证过程

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邻居认证使得路由器确认每次所收到的路由更新的源。如果关键字不匹配，就会拒绝路由更新。
　　Cisco使用两种类型的邻居认证：纯文本和MD5.
　　纯文本认证发一个关键字，这个关键字是明文传输，可被非法用户所窃取，所以不推荐使用。
　　MD5认证发一个报文摘要，而不是关键字。MD5被用来生成一个关键字的散列。这个散列是被发送的对象。MD5方式不易被非法用户所窃取。
　　这个案例中，我们在R1与R2之间使用明文认证，在R2与R3之间使用MD5认证。

[pre]// R1 //int e0/0  ip ad 192.1.1.1 255.255.255.0  ip ospf authentication-key cisco    //明文认证，关键字为ciscorouter os 1  network 192.1.1.1 0.0.0.0 area 0  area 0 authentication[/pre]

[pre]// R2 //int e0/0  ip ad 192.1.1.2 255.255.255.0  ip ospf authentication-key cisco    //明文认证，关键字为ciscoint e1/0  ip ad 193.1.1.2 255.255.255.0  ip ospf message-digest-key 1 md5 crackerrouter os 1  network 192.1.1.2 0.0.0.0 area 0  network 193.1.1.2 0.0.0.0 area 1  area 0 authentication  area 1 authentication message-digest[/pre]

[pre]// R3 //int e1/0  ip ad 193.1.1.3 255.255.255.0  ip ospf message-digest-key 1 md5 crackerrouter os 1  network 193.1.1.3 0.0.0.0 a 1  area 1 authentication message-digest[/pre]

验证过程：

[pre]r1#sh ip os int e0/0Ethernet0/0 is up, line protocol is up  Internet Address 192.1.1.1/24, Area 0  Process ID 1, Router ID 192.1.1.1, Network Type BROADCAST, Cost: 10  Transmit Delay is 1 sec, State BDR, Priority 1  Designated Router (ID) 193.1.1.2, Interface address 192.1.1.2  Backup Designated router (ID) 192.1.1.1, Interface address 192.1.1.1  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5    Hello due in 00:00:06  Index 1/1, flood queue length 0  Next 0x0(0)/0x0(0)  Last flood scan length is 1, maximum is 1  Last flood scan time is 0 msec, maximum is 0 msec  Neighbor Count is 1, Adjacent neighbor count is 1    Adjacent with neighbor 193.1.1.2  (Designated Router)  Suppress hello for 0 neighbor(s)  Simple password authentication enabledr2#sh ip os int e0/0Ethernet0/0 is up, line protocol is up  Internet Address 192.1.1.2/24, Area 0  Process ID 1, Router ID 193.1.1.2, Network Type BROADCAST, Cost: 10  Transmit Delay is 1 sec, State DR, Priority 1  Designated Router (ID) 193.1.1.2, Interface address 192.1.1.2  Backup Designated router (ID) 192.1.1.1, Interface address 192.1.1.1  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5    Hello due in 00:00:04  Index 1/1, flood queue length 0  Next 0x0(0)/0x0(0)  Last flood scan length is 1, maximum is 2  Last flood scan time is 0 msec, maximum is 0 msec  Neighbor Count is 1, Adjacent neighbor count is 1    Adjacent with neighbor 192.1.1.1  (Backup Designated Router)  Suppress hello for 0 neighbor(s)  Simple password authentication enabledr2#sh ip os int e1/0Ethernet1/0 is up, line protocol is up  Internet Address 193.1.1.2/24, Area 1  Process ID 1, Router ID 193.1.1.2, Network Type BROADCAST, Cost: 10  Transmit Delay is 1 sec, State DR, Priority 1  Designated Router (ID) 193.1.1.2, Interface address 193.1.1.2  Backup Designated router (ID) 193.1.1.3, Interface address 193.1.1.3  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5    Hello due in 00:00:03  Index 1/2, flood queue length 0  Next 0x0(0)/0x0(0)  Last flood scan length is 2, maximum is 2  Last flood scan time is 0 msec, maximum is 0 msec  Neighbor Count is 1, Adjacent neighbor count is 1    Adjacent with neighbor 193.1.1.3  (Backup Designated Router)  Suppress hello for 0 neighbor(s)  Message digest authentication enabled    Youngest key id is 1r3#sh ip os int e1/0Ethernet1/0 is up, line protocol is up  Internet Address 193.1.1.3/24, Area 1  Process ID 1, Router ID 193.1.1.3, Network Type BROADCAST, Cost: 10  Transmit Delay is 1 sec, State BDR, Priority 1  Designated Router (ID) 193.1.1.2, Interface address 193.1.1.2  Backup Designated router (ID) 193.1.1.3, Interface address 193.1.1.3  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5    Hello due in 00:00:04  Index 1/1, flood queue length 0  Next 0x0(0)/0x0(0)  Last flood scan length is 1, maximum is 2  Last flood scan time is 0 msec, maximum is 0 msec  Neighbor Count is 1, Adjacent neighbor count is 1    Adjacent with neighbor 193.1.1.2  (Designated Router)  Suppress hello for 0 neighbor(s)  Message digest authentication enabled    Youngest key id is 1[/pre]

为了更进一步理解认证过程，我们可以打开DEBUG，并将R3的MD5认证key改为5：

// R3 //debug ip ospf adjint e1/0  ip ospf message-digest-key 5 md5 crackerr3#01:16:03: OSPF: Rcv pkt from 193.1.1.2, Ethernet1/0 : Mismatch Authentication Key - No message digest key 1 on interface01:16:09: OSPF: Send with youngest Key 5r3#show ip ospf neighbor    //观察结果无法发现邻居。//认证未通过，无法与R2建立起邻居关系。

　　当我们把MD5认证KEY改回1后，认证通过。
　　第二步实验，我们把关键字进行修改：

// R3 //debug ip ospf adjint e1/0  ip ospf message-digest-key 1 md5 cuijian01:21:33: OSPF: Rcv pkt from 193.1.1.2, Ethernet1/0 : Mismatch Authentication Key - Message Digest Key 101:21:40: OSPF: Send with youngest Key 1

　　我们要在实际工作中学会使用debug这个思科排错的利器。