OSPF案例分析之如何得到正常的OSPF路由

qianyuqianxun

　　日前，笔者在工作中发现一个问题，即无法得到正常的OSPF路由。笔者现将OSPF协议排错的过程写下来，希望能与更多的朋友共享。

　　1、 现象描述

　　在下图中，两台路由器通过串口连接，在互连接口上运行OSPF协议。RouterA的以太网接口地址为111.111.111.1，且运行了OSPF协议，Router的以太网接口地址为222.222.222.1，也启用了OSPF协议。

　　RouterA的主要配置如下：

　　interface Loopback0
　　ip address 197.7.1.1 255.255.255.255
　　!
　　interface FastEthernet0/0
　　ip address 111.111.111.1 255.255.255.0
　　ip ospf cost 200
　　duplex auto
　　speed auto
　　!
　　interface Serial1/0
　　ip address 100.1.0.1 255.255.0.0
　　ip ospf network point-to-multipoint
　　ip ospf cost 200
　　serial restart-delay 0
　　!
　　router ospf 22
　　router-id 197.7.1.1
　　log-adjacency-changes
　　network 100.1.0.1 0.0.0.0 area 0
　　network 111.111.111.1 0.0.0.0 area 0
　　neighbor 100.1.0.2 cost 200

　　Router的主要配置如下：

　　interface FastEthernet0/0
　　ip address 222.222.222.1 255.255.255.0
　　ip ospf cost 200
　　duplex auto
　　speed auto
　　!
　　interface Serial1/0
　　ip address 100.1.0.2 255.255.0.0
　　ip ospf network non-broadcast
　　ip ospf cost 200
　　serial restart-delay 0
　　router ospf 22
　　router-id 197.7.1.2
　　log-adjacency-changes
　　network 100.1.0.2 0.0.0.0 area 0
　　network 222.222.222.1 0.0.0.0 area 0
　　neighbor 100.1.0.1 cost 200

　　故障现象如下：

　　在RouterA和RouterB上查看路由表，发现相互之间并没有学习到OSPF路由。
2、 显示OSPF信息

　　分别在两台路由器上查看邻居状态，显示如下：

　　RouterA#show ip ospf neighbor
　　Neighbor ID     Pri   State           Dead Time   Address         Interface
　　197.7.1.2         0   FULL/  -        00:01:38    100.1.0.2       Serial1/0
　　RouterA#show ip ospf neighbor
　　Neighbor ID     Pri   State           Dead Time   Address         Interface
　　197.7.1.1         1   FULL/BDR        00:01:54    100.1.0.1       Serial1/0

　　然后分别察看路由表，有下列显示：

　　RouterA#show ip route
　　100.0.0.0/16 is subnetted, 1 subnets
　　C       100.1.0.0 is directly connected, Serial1/0
　　197.7.1.0/32 is subnetted, 1 subnets
　　C       197.7.1.1 is directly connected, Loopback0
　　111.0.0.0/24 is subnetted, 1 subnets
　　C       111.111.111.0 is directly connected, FastEthernet0/0
　　RouterB#show ip route
　　C    222.222.222.0/24 is directly connected, FastEthernet0/0
　　100.0.0.0/16 is subnetted, 1 subnets
　　C       100.1.0.0 is directly connected, Serial1/0

　　接下来在来查看两台路由器的接口状态如下：

　　RouterA#show ip ospf interface
　　FastEthernet0/0 is up, line protocol is up
　　Internet Address 111.111.111.1/24, Area 0
　　Process ID 22, Router ID 197.7.1.1, Network Type BROADCAST, Cost: 200
　　Transmit Delay is 1 sec, State DR, Priority 1
　　Designated Router (ID) 197.7.1.1, Interface address 111.111.111.1
　　No backup designated router on this network
　　Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
　　oob-resync timeout 40
　　Hello due in 00:00:09
　　Index 2/2, flood queue length 0
　　Next 0x0(0)/0x0(0)
　　Last flood scan length is 0, maximum is 0
　　Last flood scan time is 0 msec, maximum is 0 msec
　　Neighbor Count is 0, Adjacent neighbor count is 0
　　Suppress hello for 0 neighbor(s)
　　Serial1/0 is up, line protocol is up
　　Internet Address 100.1.0.1/16, Area 0
　　Process ID 22, Router ID 197.7.1.1, Network Type POINT_TO_MULTIPOINT, Cost: 200
　　Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
　　Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
　　oob-resync timeout 120
　　Hello due in 00:00:23
　　Index 1/1, flood queue length 0
　　Next 0x0(0)/0x0(0)
　　Last flood scan length is 1, maximum is 1
　　Last flood scan time is 0 msec, maximum is 0 msec
　　Neighbor Count is 1, Adjacent neighbor count is 1
　　Adjacent with neighbor 197.7.1.2, cost is 200
　　Suppress hello for 0 neighbor(s)
　　RouterB#show ip ospf interface
　　FastEthernet0/0 is up, line protocol is up
　　Internet Address 222.222.222.1/24, Area 0
　　Process ID 22, Router ID 197.7.1.2, Network Type BROADCAST, Cost: 200
　　Transmit Delay is 1 sec, State DR, Priority 1
　　Designated Router (ID) 197.7.1.2, Interface address 222.222.222.1
　　No backup designated router on this network
　　Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
　　oob-resync timeout 40
　　Hello due in 00:00:07
　　Index 2/2, flood queue length 0
　　Next 0x0(0)/0x0(0)
　　Last flood scan length is 0, maximum is 0
　　Last flood scan time is 0 msec, maximum is 0 msec
　　Neighbor Count is 0, Adjacent neighbor count is 0
　　Suppress hello for 0 neighbor(s)
　　Serial1/0 is up, line protocol is up
　　Internet Address 100.1.0.2/16, Area 0
　　Process ID 22, Router ID 197.7.1.2, Network Type NON_BROADCAST, Cost: 200
　　Transmit Delay is 1 sec, State DR, Priority 1
　　Designated Router (ID) 197.7.1.2, Interface address 100.1.0.2
　　Backup Designated router (ID) 197.7.1.1, Interface address 100.1.0.1
　　Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
　　oob-resync timeout 120
　　Hello due in 00:00:17
　　Index 1/1, flood queue length 0
　　Next 0x0(0)/0x0(0)
　　Last flood scan length is 1, maximum is 1
　　Last flood scan time is 0 msec, maximum is 0 msec
　　Neighbor Count is 1, Adjacent neighbor count is 1
　　Adjacent with neighbor 197.7.1.1  (Backup Designated Router)
　　Suppress hello for 0 neighbor(s)

　　3、原因分析

　　从查看路由器相应接口配置和状态信息来看，RouterA和Router相连接口的OSPF网络类型并不一致，因此导致路由计算错误，无法得到正常的OSPF路由。

　　4、处理过程

　　在RouterA和RouterB上，将相应的端口网络类型改为一致，就可以学习到正常的OSPF路由。改变Router的serial1/0口的网络类型为POINT_TO_MULTIPOINT

　　改正完成后，我们在来看下两台路由器的路由表：

　　RouterA#show ip route
　　O    222.222.222.0/24 [110/400] via 100.1.0.2, 00:00:33, Serial1/0
　　100.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
　　C       100.1.0.0/16 is directly connected, Serial1/0
　　O       100.1.0.2/32 [110/200] via 100.1.0.2, 00:00:33, Serial1/0
　　111.0.0.0/24 is subnetted, 1 subnets
　　C       111.111.111.0 is directly connected, FastEthernet0/0
　　RouterB# show ip route
　　C    222.222.222.0/24 is directly connected, FastEthernet0/0
　　100.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
　　O       100.1.0.1/32 [110/200] via 100.1.0.1, 00:00:31, Serial1/0
　　C       100.1.0.0/16 is directly connected, Serial1/0
　　111.0.0.0/24 is subnetted, 1 subnets
　　O       111.111.111.0 [110/400] via 100.1.0.1, 00:00:31, Serial1/0