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)

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　　(4)OSPF的hello组播地址被ACL Block

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),