稍微對ospf的trouble shooting 總結(jié)了一下，有參考也有自己的心得。

(1)接口上沒有激活ospf

就是在network語句的時候沒有匹配清楚，比如配置了錯誤的反掩碼不對，在show ip ospf interface的時候不會顯示你希望激活的接口

使用show ip ospf interface來驗證

這時候的鄰居表是空的

R2#show ip ospf neighbor
R2#

(2)物理層或者是數(shù)據(jù)鏈路層協(xié)議down.
  
  使用show ip int brief 或者是 show int type nomber

會導致ospf packet 封裝失敗。

(3)建立鄰居的接口被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)

(4)OSPF的hello組播地址被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

這時候的鄰居關系是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鏈路上的子網(wǎng)掩碼不匹配

(6)Hello/dead 間隔不匹配
(7)認證方式或者是認證密碼不匹配

  使用debug ip ospf adj 來查看,可以自己使用不同的情況來驗證

(8)兩臺路由器處于不同的AREA

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 區(qū)域類型不匹配

這個是經(jīng)常不小心會被忘記的。

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來建立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網(wǎng)絡類型不匹配（P-TO-P 和P-TO-M網(wǎng)絡類型在hello時間間隔相同的情況下可以建立full關系，但是會缺少一條路由

）
   可以做一下相關使用驗證

(12)NBMA (Frame Relay, X.25, SMDS, and so on)網(wǎng)絡類型上沒有手動指定neighbor ip 地址

  鄰居一直都是ATTEMPT狀態(tài)

(13)在Router 兩邊的frame-relay map/dialer map語句聲明中缺少了broadcast參數(shù)

這個就不要多說了吧。

(14)接口兩邊的MTU 不匹配

在cisco ios 12.0.3中加入了對mtu的檢測，而低于這個版本的ios會忽略mtu檢測，需要查看router 的ios version，debug ip ospf adj的結(jié)

果是發(fā)現(xiàn)有大量的dbd重傳，出現(xiàn)loading的原因就是一邊的router需要對mtu進行檢測，而一邊忽略。

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

解決方法是接口命令：mtu 4470
而不是：ip mtu 4470

這時候的狀態(tài)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

還有一種mtu不匹配的情況是鄰居關系是EXSTART，因為兩邊的mtu都需要檢測，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網(wǎng)絡上需要選舉dr，而這時候兩邊的優(yōu)先級又都是0

(16)在Asynchronous Interfaces上的OSPF鄰居關系

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

解決方法是在兩個使用async default routing 或者asyn dynamic routing 接口命令

(15)兩個路由器的Router id相同，ospf的master和slave關系不能確定

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)因為router接口的物理問題而導致的 ospf packet checksum錯誤，接著就重傳的問題。

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
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