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1、OSPF邻居建立不起来的原因1)接口上没有激活ospf就是在network语句的时候没有匹配清楚，比如配置了错误的反掩码不对，在show ip ospf interface的时候不会显示你希望激活的接口使用show ip ospf interface来验证这时候的邻居表是空的>R2#show ip ospf neighborR2# (2)物理层或者是数据链路层协议down.使用show ip int brief 或者是 show int type nomber会导致ospf packet 封装失败。(3)建立邻居的接口被passive掉R2#show ip ospf interface E
2、thernet 0Ethernet0 is up, line protocol is upInternet Address 131.108.1.2/24, Area 0Process ID 1, Router ID 131.108.1.2, Network Type BROADCAST, Cost: 10Transmit Delay is 1 sec, State DR, Priority 1Designated Router (ID) 131.108.1.2, Interface address 131.108.1.2No backup designated router on this n
3、etworkTimer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5No Hellos (Passive interface)Neighbor Count is 0, Adjacent neighbor count is 0Suppress hello for 0 neighbor(s)(4)OSPF的hello组播地址被ACL BlockR1#interface Ethernet0ip address 131.108.1.1 255.255.255.0ip access-group 100 in!access-l
4、ist 100 permit tcp any anyaccess-list 100 permit udp any anyaccess-list 101 permit ip 131.108.1.0 0.0.0.255 host 224.0.0.5R2#interface Ethernet0ip address 131.108.1.2 255.255.255.0ip access-group 100 in!access-list 100 permit tcp any anyaccess-list 100 permit udp any anyaccess-list 101 permit ip 131
5、.108.1.0 0.0.0.255 host 224.0.0.5R2#debug ip packet 101 detailIP packet debugging is on (detailed) for access list 101IP: s=131.108.1.2 (Ethernet0), d=224.0.0.5, len 68, access denied, proto=89这时候的邻居关系是INITR2#show ip ospf neighborNeighbor ID Pri State Dead Time Address Interface131.108.2.1 1 INIT/-
6、00:00:33 131.108.1.1 Ethernet0R1#show access-list 101Extended IP access list 101permit ip 131.108.1.0 0.0.0.3 host 224.0.0.5 (8 matches)R1#debug ip packet 101 detailIP packet debugging is on (detailed) for access list 101R1#IP: s=131.108.1.1 (local), d=224.0.0.5 (Ethernet0), len 60, sending broad/mu
7、lticast,proto=89IP: s=131.108.1.2 (Ethernet0), d=224.0.0.5, len 82, access denied, proto=89IP: s=131.108.1.1 (local), d=224.0.0.5 (Ethernet0), len 60, sending broad/multicast,proto=89IP: s=131.108.1.2 (Ethernet0), d=224.0.0.5, len 82,access denied, proto=89(5)在broadcast链路上的子网掩码不匹配(6)Hello/dead 间隔不匹配
8、(7)认证方式或者是认证密码不匹配使用debug ip ospf adj 来查看,可以自己使用不同的情况来验证(两台路由器处于不同的AREAR1#debug ip ospf adjOSPF adjacency events debugging is onR1#OSPF: Rcv pkt from 131.108.1.2, Ethernet0, area 0.0.0.0mismatch area 0.0.0.1 in the headerR2#show log%OSPF-4-ERRRCV: Received invalid packet: mismatch area ID, from backb
9、one area must bevirtual-link butnot found from 131.108.1.1, Ethernet0(9)Stub/transit/NSSA 区域类型不匹配这个是常常不小心会被忘记的。R1#debug ip ospf adjOSPF adjacency events debugging is onR1#OSPF: Rcv hello from 131.108.0.1 area 1 from Ethernet0 131.108.1.2OSPF: Hello from 131.108.1.2 with mismatched Stub/Transit area
10、option bitR1#debug ip ospf adjOSPF adjacency events debugging is onR1#OSPF: Rcv hello from 131.108.0.1 area 1 from Ethernet0 131.108.1.2OSPF: Hello from 131.108.1.2 with mismatched NSSA option bit(10)使用secondary IP来建立OSPF adjacencyR2#interface FastEthernet0/0ip address 131.108.1.2 255.255.255.0 seco
11、ndaryip address 131.108.4.2 255.255.255.0R1#interface Ethernet0ip address 131.108.1.1 255.255.255.0R2#debug ip ospf adjOSPF adjacency events debugging is onR2#OSPF: Rcv pkt from 131.108.1.1, FastEthernet0/0, area 0.0.0.1 : src not on the same network(11)OSPF网络类型不匹配（P-TO-P 和P-TO-M网络类型在hello时间间隔相同的情况下
12、可以建立full关系，但是会缺少一条路由，可以做一下相关使用验证(12)NBMA (Frame Relay, X.25, SMDS, and so on)网络类型上没有手动指定neighbor ip 地址邻居一直都是ATTEMPT状态(13)在Router 两边的frame-relay map/dialer map语句声明中缺少了broadcast参数这个就不要多说了吧。(14)接口两边的MTU 不匹配在cisco ios 12.0.3中加入了对mtu的检测，而低于这个版本的ios会忽略mtu检测，需要查看router 的ios version，debug ip ospf adj的结果是发现有
13、大量的dbd重传，出现loading的原因就是一边的router需要对mtu进行检测，而一边忽略。R2#debug ip ospf adjOSPF adjacency events debugging is onR2#OSPF: Retransmitting request to 131.108.2.1 on Serial0OSPF: Database request to 131.108.2.1OSPF: sent LS REQ packet to 131.108.1.1, length 12OSPF: Retransmitting request to 131.108.2.1 on Ser
14、ial0解决方法是接口命令：mtu 4470而不是：ip mtu 4470这时候的状态是 loading 。R2#show ip ospf neighborNeighbor ID Pri State Dead Time Address Interface131.108.2.1 1 LOADING/- 00:00:37 131.108.1.1 Serial0还有一种mtu不匹配的情况是邻居关系是EXSTART，因为两边的mtu都需要检测，而mtu大小又不匹配.R2#show ip ospf neighborNeighbor ID Pri State Dead Time Address Inter
15、face131.108.2.1 1 EXSTART/- 00:00:33 131.108.1.1 Serial0R1#debug ip ospf adjOSPF: Retransmitting DBD to 131.108.1.2 on Serial0.1OSPF: Send DBD to 131.108.1.2 on Serial0.1 seq 0x1E55 opt 0x2 flag 0x7 len 32OSPF: Rcv DBD from 131.108.1.2 on Serial0.1 seq 0x22AB opt 0x2 flag 0x7 len 32 mtu 1500state EX
16、STARTOSPF: Nbr 131.108.1.2 has larger interface MTU(15)在broadcast网络上需要选举dr，而这时候两边的优先级又都是0(16)在Asynchronous Interfaces上的OSPF邻居关系R1#interface Async1description ASYNC LINE TO R2ip address 131.108.1.1 255.255.255.0encapsulation pppasync mode dedicateddialer in-banddialer map ip 131.108.1.2 name Router2
17、broadcastdialer-group 1ppp authentication chapR2#interface Async1description ASYNC LINE TO R1ip address 131.108.1.2 255.255.255.0encapsulation pppasync mode dedicateddialer in-banddialer map ip 131.108.1.1 name Router2 broadcastdialer-group 1ppp authentication chap解决方法是在两个使用async default routing 或者a
18、syn dynamic routing 接口命令(15)两个路由器的Router id相同，ospf的master和slave关系不能确定R2#debug ip ospf adjOSPF: Retransmitting DBD to 131.108.2.1 on Serial0OSPF: Send DBD to 131.108.2.1 on Serial0 seq 0x793 opt 0x2 flag 0x7 len 32OSPF: Rcv DBD from 131.108.2.1 on Serial0 seq 0x25F7 opt 0x2 flag 0x7 len 32 mtu 0 stat
19、eEXSTARTOSPF: First DBD and we are not SLAVE(16)因为router接口的物理问题而导致的 ospf packet checksum错误，接着就重传的问题。R2#show log%OSPF-4-ERRRCV: Received invalid packet: Bad Checksum from 131.108.1.1, Serial0%OSPF-4-ERRRCV: Received invalid packet: Bad Checksum from 131.108.1.1, Serial0R2#debug ip ospf adjOSPF adjacency events debugging is onR2#OSPF: Retransmitting request to 131.108.2.1 on Serial0OSPF: Database request to 131.108.2.1OSPF: sent LS REQ packet to 131.108.1.1, length 12OSPF: Retransmitting request to 131.108.2.1 on Serial0
