稍微对ospf的trouble shooting 总结了一下，有参考也有自己的心得。

　　(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 neighbor

R2#

　　(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 Ethernet 0

Ethernet0 is up, line protocol is up

Internet Address 131.108.1.2/24, Area 0

Process ID 1, Router ID 131.108.1.2, Network Type BROADCAST, Cost: 10

Transmit Delay is 1 sec, State DR, Priority 1

Designated Router (ID) 131.108.1.2, Interface address 131.108.1.2

No backup designated router on this network

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

No Hellos (Passive interface)

Neighbor Count is 0, Adjacent neighbor count is 0

Suppress hello for 0 neighbor(s)　　

R1#

interface Ethernet0

ip address 131.108.1.1 255.255.255.0

ip access-group 100 in

!

access-list 100 permit tcp any any

access-list 100 permit udp any any

access-list 101 permit ip 131.108.1.0 0.0.0.255 host 224.0.0.5

R2#

interface Ethernet0

ip address 131.108.1.2 255.255.255.0

ip access-group 100 in

!

access-list 100 permit tcp any any

access-list 100 permit udp any any

access-list 101 permit ip 131.108.1.0 0.0.0.255 host 224.0.0.5

R2#debug ip packet 101 detail

IP packet debugging is on (detailed) for access list 101

IP: 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INIT

R2#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

131.108.2.1 1 INIT/- 00:00:33 131.108.1.1 Ethernet0

R1#show access-list 101

Extended IP access list 101

permit ip 131.108.1.0 0.0.0.3 host 224.0.0.5 (8 matches)

R1#debug ip packet 101 detail

IP packet debugging is on (detailed) for access list 101

R1#

IP: s=131.108.1.1 (local), d=224.0.0.5 (Ethernet0), len 60, sending broad/multicast,

proto

=89

IP: s=131.108.1.2 (Ethernet0), d=224.0.0.5, len 82, access denied, proto=89

IP: s=131.108.1.1 (local), d=224.0.0.5 (Ethernet0), len 60, sending broad/multicast,

proto

=89

IP: 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

    (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　　

R1#debug ip ospf adj

OSPF adjacency events debugging is on

R1#

OSPF: Rcv pkt from 131.108.1.2, Ethernet0, area 0.0.0.0

mismatch area 0.0.0.1 in the header

R2#show log

%OSPF-4-ERRRCV: Received invalid packet: mismatch area ID, from backbone area must be

virtual-link but not 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。-v-

R1#debug ip ospf adj

OSPF adjacency events debugging is on

R1#

OSPF: Rcv hello from 131.108.0.1 area 1 from Ethernet0 131.108.1.2

OSPF: Hello from 131.108.1.2 with mismatched Stub/Transit area option bit

R1#debug ip ospf adj

OSPF adjacency events debugging is on

R1#

OSPF: Rcv hello from 131.108.0.1 area 1 from Ethernet0 131.108.1.2

OSPF: Hello from 131.108.1.2 with mismatched NSSA option bit

　　　(10)使用secondary IP来建立OSPF adjacency

R2#

interface FastEthernet0/0

ip address 131.108.1.2 255.255.255.0 secondary

ip address 131.108.4.2 255.255.255.0

R1#

interface Ethernet0

ip address 131.108.1.1 255.255.255.0

R2#debug ip ospf adj

OSPF adjacency events debugging is on

R2#

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

(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 adj

OSPF adjacency events debugging is on

R2#

OSPF: Retransmitting request to 131.108.2.1 on Serial0

OSPF: Database request to 131.108.2.1

OSPF: sent LS REQ packet to 131.108.1.1, length 12

OSPF: Retransmitting request to 131.108.2.1 on Serial0

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 neighbor

Neighbor ID Pri State Dead Time Address Interface

131.108.2.1 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 neighbor

Neighbor ID Pri State Dead Time Address Interface

131.108.2.1 1 EXSTART/- 00:00:33 131.108.1.1 Serial0

R1#debug ip ospf adj

OSPF: Retransmitting DBD to 131.108.1.2 on Serial0.1

OSPF: Send DBD to 131.108.1.2 on Serial0.1 seq 0x1E55 opt 0x2 flag 0x7 len 32

OSPF: Rcv DBD from 131.108.1.2 on Serial0.1 seq 0x22AB opt 0x2 flag 0x7 len 32 mtu 1500

state EXSTART

OSPF: 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 Async1

description ASYNC LINE TO R2

ip address 131.108.1.1 255.255.255.0

encapsulation ppp

async mode dedicated

dialer in-band

dialer map ip 131.108.1.2 name Router2 broadcast

dialer-group 1

ppp authentication chap

R2#

interface Async1

description ASYNC LINE TO R1

ip address 131.108.1.2 255.255.255.0

encapsulation ppp

async mode dedicated

dialer in-band

dialer map ip 131.108.1.1 name Router2 broadcast

dialer-group 1

ppp authentication chap

　　解决方法是在两个使用async default routing 或者asyn 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 adj

OSPF: Retransmitting DBD to 131.108.2.1 on Serial0

OSPF: Send DBD to 131.108.2.1 on Serial0 seq 0x793 opt 0x2 flag 0x7 len 32

OSPF: Rcv DBD from 131.108.2.1 on Serial0 seq 0x25F7 opt 0x2 flag 0x7 len 32 mtu 0 state

EXSTART

OSPF: 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, Serial0

R2#debug ip ospf adj

R2#

OSPF: Retransmitting request to 131.108.2.1 on Serial0

OSPF: Database request to 131.108.2.1