在Boradcast网络中建立OSPF邻居关系
实验目的：观察在广播网络中，OSPF建立邻接关系的过程
实验拓扑及设备需求
拓扑：
需求：配置3台路由器的以太网接口，参与OSPF，使3台路由器建立邻接关系
测试：
1.使用show命令观察参与ospf的接口，及ospf建立邻接关系的过程
R1#show ip ospf interface brief
Interface PID Area IP Address/Mask Cost State Nbrs F/C
Et0 1 0 10.1.1.1/24 10 DROTH 2/2
R2#show ip ospf interface brief
Interface PID Area IP Address/Mask Cost State Nbrs F/C
Et0 1 0 10.1.1.2/24 10 BDR 2/2
Rack12R3#show ip ospf interface brief
Interface PID Area IP Address/Mask Cost State Nbrs F/C
Et0/0 1 0 10.1.1.3/24 10 DR 2/2
可以看到，在缺省情况下，各个路由器的接口优先级相同，所以选举DR、BDR时比较的是接口IP地址。R3作为DR，R2作为BDR，R1为DROTHER。
2.使用show命令关系ospf邻接关系
R1#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
10.1.1.2 1 FULL/BDR 00:00:32 10.1.1.2 Ethernet0
10.1.1.3 1 FULL/DR 00:00:30 10.1.1.3 Ethernet0
R2#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
10.1.1.1 1 FULL/DROTHER 00:00:35 10.1.1.1 Ethernet0
10.1.1.3 1 FULL/DR 00:00:37 10.1.1.3 Ethernet0
R3#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
10.1.1.1 1 FULL/DROTHER 00:00:31 10.1.1.1 Ethernet0
10.1.1.2 1 FULL/BDR 00:00:36 10.1.1.2 Ethernet0
可以看到，在广播网络中，ospf建立邻接关系不需要管理员的干涉，而是自动建立的。
3.使用debug观察整个邻接关系的建立过程
R1#debug ip ospf event
*Mar 1 00:26:54.327: OSPF: Send hello to 224.0.0.5 area 0 on Ethernet0 from 10.
1.1.1 （为224.0.0.5为目的发送hello包，发现邻居）
*Mar 1 00:26:54.811: OSPF: Rcv hello from 10.1.1.2 area 0 from Ethernet0 10.1.1
.2 （接收到邻居10.1.1.2发送的hello包）
*Mar 1 00:26:54.815: OSPF:2 Way Communication to 10.1.1.2 on Ethernet0, state
2WAY （10.1.1.2的hello包中的邻居列表包含自己的Router ID）
*Mar 1 00:26:54.819: OSPF: Backup seen Event before WAIT timer on Ethernet0
*Mar 1 00:26:54.823: OSPF: DR/BDR election on Ethernet0
（2-Way状态后，广播网络需要选举DR、BDR）
*Mar 1 00:26:54.823: OSPF: Elect BDR 10.1.1.2
*Mar 1 00:26:54.827: OSPF: Elect DR 10.1.1.2
*Mar 1 00:26:54.827: DR: 10.1.1.2 (Id) BDR: 10.1.1.2 (Id)
*Mar 1 00:26:54.831: OSPF: Send DBD to 10.1.1.2 on Ethernet0 seq 0x116B opt 0x5
2 flag 0x7 len 32
*Mar 1 00:26:54.839: OSPF: End of hello processing
*Mar 1 00:26:54.843: OSPF: Rcv hello from 10.1.1.3 area 0 from Ethernet0 10.1.1
.3
*Mar 1 00:26:54.847: OSPF: 2 Way Communication to 10.1.1.3 on Ethernet0, state
2WAY
*Mar 1 00:26:54.851: OSPF: Neighbor change Event on interface Ethernet0
*Mar 1 00:26:54.851: OSPF: DR/BDR election on Ethernet0
*Mar 1 00:26:54.855: OSPF: Elect BDR 10.1.1.2
*Mar 1 00:26:54.855: OSPF: Elect DR 10.1.1.3
*Mar 1 00:26:54.859: DR: 10.1.1.3 (Id) BDR: 10.1.1.2 (Id)
*Mar 1 00:26:54.863: OSPF: Send DBD to 10.1.1.3 on Ethernet0 seq 0x4EC opt 0x52
flag 0x7 len 32
*Mar 1 00:26:54.867: OSPF: Remember old DR 10.1.1.2 (id)
*Mar 1 00:26:54.871: OSPF: Neighbor change Event on interface Ethernet0
*Mar 1 00:26:54.871: OSPF: DR/BDR election on Ethernet0
*Mar 1 00:26:54.871: OSPF: Elect BDR 10.1.1.2
*Mar 1 00:26:54.875: OSPF: Elect DR 10.1.1.3
*Mar 1 00:26:54.879:DR: 10.1.1.3 (Id) BDR: 10.1.1.2 (Id)
（选举结果，若优先级相同，则IP地址大的为DR或BDR）
*Mar 1 00:26:54.879: OSPF: End of hello processing
（2-Way状态结束，开始发送DD包）
*Mar 1 00:26:54.887: OSPF:Rcv DBD from 10.1.1.2 on Ethernet0 seq 0x1345 opt 0x
52 flag 0x7 len 32 mtu 1500 state EXSTART
（发送数据库描述包，确认同步的主从关系进入ExStart状态）
*Mar 1 00:26:54.891: OSPF:NBR Negotiation Done. We are the SLAVE
（协商完毕，IP地址低的为从）
*Mar 1 00:26:54.891: OSPF: Send DBD to 10.1.1.2 on Ethernet0 seq 0x1345 opt 0x5
2 flag 0x2 len 52
*Mar 1 00:26:54.899: OSPF: Rcv DBD from 10.1.1.3 on Ethernet0 seq 0x3B0 opt 0x5
2 flag 0x7 len 32 mtu 1500 state EXSTART
*Mar 1 00:26:54.903: OSPF: NBR Negotiation Done. We are the SLAVE
*Mar 1 00:26:54.907: OSPF: Send DBD to 10.1.1.3 on Ethernet0 seq 0x3B0 opt 0x52
flag 0x2 len 52
*Mar 1 00:26:54.915: OSPF:Rcv DBD from 10.1.1.2 on Ethernet0 seq 0x1346 opt 0x
52 flag 0x3 len 92 mtu 1500 state EXCHANGE
（从10.1.1.2收到DD包，确认数据库是否相同,进入Exchange状态）
*Mar 1 00:26:54.919: OSPF: Send DBD to 10.1.1.2 on Ethernet0 seq 0x1346 opt 0x5
2 flag 0x0 len 32
*Mar 1 00:26:54.927: OSPF: Database request to 10.1.1.2
*Mar 1 00:26:54.927: OSPF: sent LS REQ packet to 10.1.1.2, length 36
（向10.1.1.2发送链路状态请求包，进入loading状态）
*Mar 1 00:26:54.999: OSPF: Rcv DBD from 10.1.1.3 on Ethernet0 seq 0x3B1 opt 0x5
2 flag 0x3 len 92 mtu 1500 state EXCHANGE
*Mar 1 00:26:55.003: OSPF: Send DBD to 10.1.1.3 on Ethernet0 seq 0x3B1 opt 0x52
flag 0x0 len 32
*Mar 1 00:26:55.011: OSPF: Database request to 10.1.1.3
*Mar 1 00:26:55.015: OSPF: sent LS REQ packet to 10.1.1.3, length 36
*Mar 1 00:26:55.019: OSPF: Rcv DBD from 10.1.1.2 on Ethernet0 seq 0x1347 opt 0x
52 flag 0x1 len 32 mtu 1500 state EXCHANGE
*Mar 1 00:26:55.019: OSPF: Exchange Done with 10.1.1.2 on Ethernet0
*Mar 1 00:26:55.023: OSPF: Send DBD to 10.1.1.2 on Ethernet0 seq 0x1347 opt 0x5
2 flag 0x0 len 32
*Mar 1 00:26:55.035: OSPF: Synchronized with 10.1.1.2 on Ethernet0, state FULL
（进入Full状态，开始同步数据库）
*Mar 1 00:26:55.039: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.1.2 on Ethernet0 from
LOADING to FULL, Loading Done
*Mar 1 00:26:55.047: OSPF: Rcv DBD from 10.1.1.3 on Ethernet0 seq 0x3B2 opt 0x5
2 flag 0x1 len 32 mtu 1500 state EXCHANGE
*Mar 1 00:26:55.051: OSPF: Exchange Done with 10.1.1.3 on Ethernet0
*Mar 1 00:26:55.051: OSPF: Synchronized with 10.1.1.3 on Ethernet0, state FULL
*Mar 1 00:26:55.055: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.1.3 on Ethernet0 from
LOADING to FULL, Loading Done实验总结：在广播网络中，OSPF通过以组地址224.0.0.5为目的发送hello包，自动发现邻居，并选举DR、BDR，所有非DR与DR、BDR建立Full邻接关系，同步数据库。
https://blog.51cto.com/zhuorong/1048319
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