广播多路访问链路的(OSPF)

 

 

步骤:

1)步骤1:配置路由器R1

R1(config)#router ospf 1

R1(config-router)#router-id 1.1.1 .1

R1(config-router)#network 1.1.1 .1 0.0.0.255 area 0

R1(config-router)#network 192.168.1.0 0.0.0 .255 area 0

2)步骤2:配置路由器R2

R2(config)#router ospf 1

R2(config-router)#router-id 2.2.2 .2

R2(config-router)#network 2.2.2 .2 0.0.0.255 area 0

R2(config-router)#network 192.168.1.0 0.0.0 .255 area 0

3)步骤3:配置路由器R3

R3(config)#router ospf 1

R3(config-router)#router-id 3.3.3 .3

R3(config-router)#network 3.3.3 .3 0.0.0.255 area 0

R3(config-router)#network 192.168.1.0 0.0.0 .255 area 0

4)步骤4:配置路由器R4

R4(config)#router ospf 1

R4(config-router)#router-id 4.4.4 .4

R4(config-router)#network 4.4.4 .4 0.0.0.255 area 0

R4(config-router)#network 192.168.1.0 0.0.0 .255 area 0

2show ip ospf neighbor:查看ospf邻居关系

R1#show ip ospf neighbor

 

Neighbor ID     Pri   State           Dead Time   Address         Interface

2.2.2 .2           1   FULL/BDR        00:00:36    192.168.1.2     Ethernet0/0

3.3.3 .3           1   FULL/DROTHER    00:00:39    192.168.1.3     Ethernet0/0

4.4.4 .4           1   FULL/DROTHER    00:00:39    192.168.1.4     Ethernet0/0

以上输出表明在该广播多路访问网络中,R1 DR,R2 BDR,R3 R4 DROTHER

【技术要点】

1)为了避免路由器之间建立完全邻接关系而引起的大量开销,OSPF 要求在多路访问的网络中选举一个DR,每个路由器都与之建立邻接关系。选举DR 的同时也选举出一个BDR,在DR 失效的时候,BDR 担负起DR 的职责,而且所有其它路由器只与DR BDR 建立邻接关系;

2DR BDR 有它们自己的组播地址224.0.0.6

3DR BDR 的选举是以各个网络为基础的,也就是说DR BDR 选举是一个路由器的接口特性,而不是整个路由器的特性;

4DR 选举的原则:

① 首要因素是时间,最先启动的路由器被选举成DR

② 如果同时启动,或者重新选举,则看接口优先级(范围为0-255),优先级最高的被选举成DR,默认情况下,多路访问网络的接口优先级为1,点到点网络接口优先级为0,修改接口优先级的命令是“ ip ospf priority”,如果接口的优先级被设置为0,那么该接口将不参与DR 选举;

③ 如果前两者相同,最后看路由器ID,路由器ID 最高的被选举成DR

5DR 选举是非抢占的,除非人为地重新选举。重新选举DR 的方法有两种,一是路由器重新启动,二是执行“clear ip ospf process”命令。

3debug ip ospf adj:显示OSPF 邻接关系创建或中断的过程

R2#debug ip ospf adj

OSPF adjacency events debugging is on

R2#clear ip ospf process

Reset ALL OSPF processes? [no]: y

*Mar  1 00:18:23.543: OSPF: Interface Ethernet0/0 going Down

*Mar  1 00:18:23.543: OSPF: 2.2.2 .2 address 192.168.1.2 on Ethernet0/0 is dead,

state DOWN

*Mar  1 00:18:23.543: OSPF: Neighbor change Event on interface Ethernet0/0

*Mar  1 00:18:23.543: OSPF: DR/BDR election on Ethernet0/0

*Mar  1 00:18:23.547: OSPF: Elect BDR 4.4.4 .4

*Mar  1 00:18:23.547: OSPF: Elect DR 1.1.1 .1

*Mar  1 00:18:23.547: OSPF: Elect BDR 4.4.4 .4

*Mar  1 00:18:23.547: OSPF: Elect DR 1.1.1 .1

*Mar  1 00:18:23.547:        DR: 1.1.1 .1 (Id)   BDR: 4.4.4.4 (Id)

*Mar  1 00:18:23.551: OSPF: Reset adjacency with 3.3.3 .3 on Ethernet0/0, state 2

WAY

*Mar  1 00:18:23.551: OSPF: 1.1.1 .1 address 192.168.1.1 on Ethernet0/0 is dead,

state DOWN

*Mar  1 00:18:23.551: %OSPF-5-ADJCHG: Process 1, Nbr 1.1.1 .1 on Ethernet0/0 from

 FULL to DOWN, Neighbor Down: Interface down or detached

*Mar  1 00:18:23.555: OSPF: Neighbor change Event on interface Ethernet0/0

*Mar  1 00:18:23.555: OSPF: DR/BDR election on Ethernet0/0

*Mar  1 00:18:23.555: OSPF: Elect BDR 4.4.4 .4

*Mar  1 00:18:28.803: OSPF: Rcv LS UPD from 1.1.1 .1 on Ethernet0/0 length 76 LSA

 count 100:18:23.555:        DR: 4.4.4 .4 (Id)   BDR: 4.4.4.4 (Id)

*Mar  1 00:18:29.127: OSPF: Rcv LS UPD from 1.1.1 .1 on Ethernet0/0 length 76 LSA

 count 100:18:23.559: OSPF: 3.3.3 .3 address 192.168.1.3 on Ethernet0/0 is dead,

*Mar  1 00:18:29.179: OSPF: Rcv LS UPD from 4.4.4 .4 on Ethernet0/0 length 76 LSA

 count 100:18:23.559: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3 .3 on Ethernet0/0 from

*Mar  1 00:18:29.571: OSPF: Build router LSA for area 0, router ID 2.2.2 .2, seq

0x80000004:18:23.559: OSPF: Neighbor change Event on interface Ethernet0/0

*Mar  1 00:18:29.611: OSPF: Rcv LS UPD from 1.1.1 .1 on Ethernet0/0 length 76 LSA

 count 100:18:23.563: OSPF: Elect BDR 4.4.4 .4

*Mar  1 00:18:31.475: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on Ethe

rnet0/0 (not full duplex), with Router FastEthernet0/2 (full duplex).

*Mar  1 00:18:23.563: OSPF: 4.4.4 .4 address 192.168.1.4 on Ethernet0/0 is dead,

state DOWN

*Mar  1 00:18:23.567: %OSPF-5-ADJCHG: Process 1, Nbr 4.4.4 .4 on Ethernet0/0 from

 FULL to DOWN, Neighbor Down: Interface down or detached

*Mar  1 00:18:23.567: OSPF: Neighbor change Event on interface Ethernet0/0

*Mar  1 00:18:23.567: OSPF: DR/BDR election on Ethernet0/0

*Mar  1 00:18:23.571: OSPF: Elect BDR 0.0.0 .0

*Mar  1 00:18:23.571: OSPF: Elect DR 0.0.0 .0

*Mar  1 00:18:23.571:        DR: none    BDR: none

*Mar  1 00:18:23.571: OSPF: Remember old DR 4.4.4 .4 (id)

*Mar  1 00:18:23.571: OSPF: Interface Loopback0 going Down

*Mar  1 00:18:23.575: OSPF: 2.2.2 .2 address 2.2.2.2 on Loopback0 is dead, state

DOWN

*Mar  1 00:18:23.655: OSPF: Interface Ethernet0/0 going Up

*Mar  1 00:18:23.655: OSPF: Interface Loopback0 going Up

*Mar  1 00:18:23.675: OSPF: 2 Way Communication to 4.4.4 .4 on Ethernet0/0, state

 2WAY

*Mar  1 00:18:23.679: OSPF: Backup seen Event before WAIT timer on Ethernet0/0

*Mar  1 00:18:23.679: OSPF: DR/BDR election on Ethernet0/0

*Mar  1 00:18:23.679: OSPF: Elect BDR 4.4.4 .4

*Mar  1 00:18:23.679: OSPF: Elect DR 4.4.4 .4

*Mar  1 00:18:23.679:        DR: 4.4.4 .4 (Id)   BDR: 4.4.4.4 (Id)

*Mar  1 00:18:23.683: OSPF: Send DBD to 4.4.4 .4 on Ethernet0/0 seq 0xE02 opt 0x5

2 flag 0x7 len 32

*Mar  1 00:18:23.683: OSPF: 2 Way Communication to 1.1.1 .1 on Ethernet0/0, state

 2WAY

*Mar  1 00:18:23.687: OSPF: Neighbor change Event on interface Ethernet0/0

*Mar  1 00:18:23.687: OSPF: DR/BDR election on Ethernet0/0

*Mar  1 00:18:23.687: OSPF: Elect BDR 4.4.4 .4

*Mar  1 00:18:23.687: OSPF: Elect DR 1.1.1 .1

*Mar  1 00:18:23.687:        DR: 1.1.1 .1 (Id)   BDR: 4.4.4.4 (Id)

*Mar  1 00:18:23.691: OSPF: Send DBD to 1.1.1 .1 on Ethernet0/0 seq 0x 224A opt 0x

52 flag 0x7 len 32

*Mar  1 00:18:23.691: OSPF: Remember old DR 4.4.4 .4 (id)

*Mar  1 00:18:23.691: OSPF: Neighbor change Event on interface Ethernet0/0

*Mar  1 00:18:23.691: OSPF: DR/BDR election on Ethernet0/0

*Mar  1 00:18:23.695: OSPF: Elect BDR 4.4.4 .4

*Mar  1 00:18:23.695: OSPF: Elect DR 1.1.1 .1

*Mar  1 00:18:23.695:        DR: 1.1.1 .1 (Id)   BDR: 4.4.4.4 (Id)

*Mar  1 00:18:23.695: OSPF: 2 Way Communication to 3.3.3 .3 on Ethernet0/0, state

 2WAY

*Mar  1 00:18:23.699: OSPF: Neighbor change Event on interface Ethernet0/0

*Mar  1 00:18:23.699: OSPF: DR/BDR election on Ethernet0/0

*Mar  1 00:18:23.699: OSPF: Elect BDR 4.4.4 .4

*Mar  1 00:18:23.699: OSPF: Elect DR 1.1.1 .1

*Mar  1 00:18:23.699:        DR: 1.1.1 .1 (Id)   BDR: 4.4.4.4 (Id)

*Mar  1 00:18:23.703: OSPF: Neighbor change Event on interface Ethernet0/0

*Mar  1 00:18:23.703: OSPF: DR/BDR election on Ethernet0/0

*Mar  1 00:18:23.703: OSPF: Elect BDR 4.4.4 .4

*Mar  1 00:18:23.703: OSPF: Elect DR 1.1.1 .1

*Mar  1 00:18:23.703:        DR: 1.1.1 .1 (Id)   BDR: 4.4.4.4 (Id)

*Mar  1 00:18:23.719: OSPF: Rcv DBD from 4.4.4 .4 on Ethernet0/0 seq 0xD85 opt 0x

以上的输出表明:

DR 重新选举的过程和结果,新的DR R1BDR R4

② 在OSPF 邻接关系建立的过程中,接口的状态的变化包括DOWN2 WayEXSTART

EXCHANGELoading FULL

 

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