廣播多路訪問鏈路的（OSPF）

時間 2020-06-15

標籤廣播多路訪問鏈路 ospf 简体版

原文原文鏈接

步驟：網絡

（1）步驟1：配置路由器R1 ide

R1(config)#router ospf 1 oop

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

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

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

（2）步驟2：配置路由器R2 debug

R2(config)#router ospf 1 orm

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

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

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

（3）步驟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）步驟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

（2）show ip ospf neighbor：查看ospf鄰居關係

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

以上輸出代表在該廣播多路訪問網絡中，R1 是DR,R2 是BDR,R3 和R4 爲DROTHER。

【技術要點】

（1）爲了不路由器之間創建徹底鄰接關係而引發的大量開銷，OSPF 要求在多路訪問的網絡中選舉一個DR，每一個路由器都與之創建鄰接關係。選舉DR 的同時也選舉出一個BDR，在DR 失效的時候，BDR 擔負起DR 的職責，並且全部其它路由器只與DR 和BDR 創建鄰接關係；

（2）DR 和BDR 有它們本身的組播地址224.0.0.6；

（3）DR 和BDR 的選舉是以各個網絡爲基礎的，也就是說DR 和BDR 選舉是一個路由器的接口特性，而不是整個路由器的特性；

（4）DR 選舉的原則：

① 首要因素是時間，最早啓動的路由器被選舉成DR；

② 若是同時啓動，或者從新選舉，則看接口優先級（範圍爲0-255），優先級最高的被選舉成DR，默認狀況下，多路訪問網絡的接口優先級爲1，點到點網絡接口優先級爲0，修改接口優先級的命令是「 ip ospf priority」，若是接口的優先級被設置爲0，那麼該接口將不參與DR 選舉；

③ 若是前二者相同，最後看路由器ID，路由器ID 最高的被選舉成DR；

（5）DR 選舉是非搶佔的，除非人爲地從新選舉。從新選舉DR 的方法有兩種，一是路由器從新啓動，二是執行「clear ip ospf process」命令。

（3）debug ip ospf adj：顯示OSPF 鄰接關係建立或中斷的過程

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

以上的輸出代表：

① DR 從新選舉的過程和結果，新的DR 是R1，BDR 是R4；

② 在OSPF 鄰接關係創建的過程當中，接口的狀態的變化包括DOWN、2 Way、EXSTART、

EXCHANGE、Loading 和FULL。

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