驗證OSPF鄰居認證的過程

作者：佚名 2009-06-09 11:03:15

鄰居認證使得路由器確認每次所收到的路由更新的源。如果關鍵字不匹配，就會拒絕路由更新。

Cisco使用兩種類型的鄰居認證：純文本和MD5。

純文本認證發一個關鍵字，這個關鍵字是明文傳輸，可被非法用戶所竊取，所以不推薦使用。

MD5認證發一個報文摘要，而不是關鍵字。MD5被用來生成一個關鍵字的散列。這個散列是被發送的對象。MD5方式不易被非法用戶所竊取。

這個案例中，我們在R1與R2之間使用明文認證，在R2與R3之間使用MD5認證。

// R1 //

int e0/0
ip ad 192.1.1.1 255.255.255.0
ip ospf authentication-key cisco//明文認證，關鍵字為cisco

router os 1
network 192.1.1.1 0.0.0.0 area 0
area 0 authentication

// R2 //

int e0/0
ip ad 192.1.1.2 255.255.255.0
ip ospf authentication-key cisco//明文認證，關鍵字為cisco

int e1/0
ip ad 193.1.1.2 255.255.255.0
ip ospf message-digest-key 1 md5 cracker

router 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

// R3 //

int e1/0
ip ad 193.1.1.3 255.255.255.0
ip ospf message-digest-key 1 md5 cracker

router os 1
network 193.1.1.3 0.0.0.0 a 1
area 1 authentication message-digest

驗證過程：

r1#sh ip os int e0/0
Ethernet0/0 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 enabled

r2#sh ip os int e0/0
Ethernet0/0 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 enabled

r2#sh ip os int e1/0
Ethernet1/0 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 1

r3#sh ip os int e1/0
Ethernet1/0 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

為了更進一步理解認證過程，我們可以打開DEBUG，并將R3的MD5認證key改為5：
// R3 //

debug ip ospf adj

int e1/0
ip ospf message-digest-key 5 md5 cracker

r3#
01:16:03: OSPF: Rcv pkt from 193.1.1.2, Ethernet1/0 : Mismatch Authentication Key - No message digest key 1 on interface
01:16:09: OSPF: Send with youngest Key 5

r3#show ip ospf neighbor//觀察結果無法發現鄰居。

//認證未通過，無法與R2建立起鄰居關系。

當我們把MD5認證KEY改回1后，認證通過。

第二步實驗，我們把關鍵字進行修改：
// R3 //

debug ip ospf adj

int e1/0
ip ospf message-digest-key 1 md5 cuijian

01:21:33: OSPF: Rcv pkt from 193.1.1.2, Ethernet1/0 : Mismatch Authentication Key - Message Digest Key 1
01:21:40: OSPF: Send with youngest Key 1

我們要在實際工作中學會使用debug這個思科排錯的利器。

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責任編輯：夏雨來源： 56CTO

OSPF 鄰居認證路由器