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)
(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
#p#
R5:
router bgp 200
network 1.0.0.0
neighbor 192.168.3.1 remote-as 300
neighbor 192.168.3.1 route-map set_med_200 out
neighbor 192.168.4.1 remote-as 300
neighbor 192.168.4.1 route-map set_med_100 out
access-list 1 permit 1.0.0.0
route-map set_med_200 permit 10
match ip address 1
set metric 200
route-map set_med_100 permit 10
match ip address 1
set metric 100
默认情况下:
R4#s ip bgp
BGP table version is 6, local router ID is 192.168.3.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* i1.0.0.0 192.168.1.1 150 100 0 100 i
* i 192.168.4.2 100 100 0 200 i
*> 192.168.3.2 200 0 200 i
*>i192.168.1.0 192.168.2.1 0 100 0 i
*>i192.168.4.0 192.168.5.1 0 100 0 i
R4(config-router)#bgp deterministic-med
R4#s ip bgp
BGP table version is 6, local router ID is 192.168.3.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i1.0.0.0 192.168.1.1 150 100 0 100 i
* i 192.168.4.2 100 100 0 200 i
* 192.168.3.2 200 0 200 i
*>i192.168.1.0 192.168.2.1 0 100 0 i
*>i192.168.4.0 192.168.5.1 0 100 0 i
R4(config-router)#bgp always-compare-med
R4#s ip bgp
BGP table version is 6, local router ID is 192.168.3.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* i1.0.0.0 192.168.1.1 150 100 0 100 i
*>i 192.168.4.2 100 100 0 200 i
* 192.168.3.2 200 0 200 i
*>i192.168.1.0 192.168.2.1 0 100 0 i
*>i192.168.4.0 192.168.5.1 0 100 0 i
R4#s ip bgp 1.0.0.0
BGP routing table entry for 1.0.0.0/8, version 6
Paths: (3 available, best #2, table Default-IP-Routing-Table)
Advertised to non peer-group peers:
192.168.3.2
100
192.168.1.1 (metric 5) from 192.168.2.1 (192.168.2.1)
Origin IGP, metric 150, localpref 100, valid, internal
200
192.168.4.2 (metric 10) from 192.168.5.1 (192.168.5.1)
Origin IGP, metric 100, localpref 100, valid, internal, best
200
192.168.3.2 from 192.168.3.2 (1.1.1.1)
Origin IGP, metric 200, localpref 100, valid, external
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
(8)两台路由器处于不同的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 区域类型不匹配
这个是常常不小心会被忘记的。
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
#p#
(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
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
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