在Boradcast網絡中建立OSPF鄰居關係
實驗目的：觀察在廣播網絡中，OSPF建立鄰接關係的過程
實驗拓撲及設備需求
拓撲：
需求：配置3臺路由器的以太網接口，參與OSPF，使3臺路由器建立鄰接關係
測試：
1.使用show命令觀察參與ospf的接口，及ospf建立鄰接關係的過程
R1#show ip ospf interface brief
Interface PID Area IP Address/Mask
Et0 1 0
R2#show ip ospf interface brief
Interface PID Area IP Address/Mask
Et0 1 0
Rack12R3#show ip ospf interface brief
Interface PID Area IP Address/Mask
Et0/0 1 0
可以看到，在缺省情況下，各個路由器的接口優先級相同，所以選舉DR、BDR時比較的是接口IP地址。R3作爲DR，R2作爲BDR，R1爲DROTHER。
2.使用show命令關係ospf鄰接關係
R1#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
R2#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
R3#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
可以看到，在廣播網絡中，ospf建立鄰接關係不需要管理員的干涉，而是自動建立的。
3.使用debug觀察整個鄰接關係的建立過程
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.
*Mar 1 00:26:54.811: OSPF: Rcv hello from
.2 （接收到鄰居10.1.1.2發送的hello包）
*Mar 1 00:26:54.815: OSPF: 2 Way Communication to
2WAY （
*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狀態後，廣播網絡需要選舉DR、BDR）
*Mar 1 00:26:54.823: OSPF: Elect BDR
*Mar 1 00:26:54.827: OSPF: Elect DR
*Mar 1 00:26:54.827: DR:
*Mar 1 00:26:54.831: OSPF: Send DBD to
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
.3
*Mar 1 00:26:54.847: OSPF: 2 Way Communication to
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
*Mar 1 00:26:54.855: OSPF: Elect DR
*Mar 1 00:26:54.859: DR:
*Mar 1 00:26:54.863: OSPF: Send DBD to
flag 0x7 len 32
*Mar 1 00:26:54.867: OSPF: Remember old DR
*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
*Mar 1 00:26:54.875: OSPF: Elect DR
*Mar 1 00:26:54.879: DR:
（選舉結果，若優先級相同，則IP地址大的爲DR或BDR）
*Mar 1 00:26:54.879: OSPF: End of hello processing
（2-Way狀態結束，開始發送DD包）
*Mar 1 00:26:54.887: OSPF: Rcv DBD from
52 flag 0x7 len 32 mtu 1500 state EXSTART
（發送數據庫描述包，確認同步的主從關係進入ExStart狀態）
*Mar 1 00:26:54.891: OSPF: NBR Negotiation Done. We are the SLAVE
（協商完畢，IP地址低的爲從）
*Mar 1 00:26:54.891: OSPF: Send DBD to
2 flag 0x2 len 52
*Mar 1 00:26:54.899: OSPF: Rcv DBD from
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
flag 0x2 len 52
*Mar 1 00:26:54.915: OSPF: Rcv DBD from
52 flag 0x3 len 92 mtu 1500 state EXCHANGE
（從
*Mar 1 00:26:54.919: OSPF: Send DBD to
2 flag 0x0 len 32
*Mar 1 00:26:54.927: OSPF: Database request to
*Mar 1 00:26:54.927: OSPF: sent LS REQ packet to
（向
*Mar 1 00:26:54.999: OSPF: Rcv DBD from
2 flag 0x3 len 92 mtu 1500 state EXCHANGE
*Mar 1 00:26:55.003: OSPF: Send DBD to
flag 0x0 len 32
*Mar 1 00:26:55.011: OSPF: Database request to
*Mar 1 00:26:55.015: OSPF: sent LS REQ packet to
*Mar 1 00:26:55.019: OSPF: Rcv DBD from
52 flag 0x1 len 32 mtu 1500 state EXCHANGE
*Mar 1 00:26:55.019: OSPF: Exchange Done with
*Mar 1 00:26:55.023: OSPF: Send DBD to
2 flag 0x0 len 32
*Mar 1 00:26:55.035: OSPF: Synchronized with
（進入Full狀態，開始同步數據庫）
*Mar 1 00:26:55.039: %OSPF-5-ADJCHG: Process 1, Nbr
LOADING to FULL, Loading Done
*Mar 1 00:26:55.047: OSPF: Rcv DBD from
2 flag 0x1 len 32 mtu 1500 state EXCHANGE
*Mar 1 00:26:55.051: OSPF: Exchange Done with
*Mar 1 00:26:55.051: OSPF: Synchronized with
*Mar 1 00:26:55.055: %OSPF-5-ADJCHG: Process 1, Nbr
LOADING to FULL, Loading Done
實驗總結：在廣播網絡中，OSPF通過以組地址224.0.0.5爲目的發送hello包，自動發現鄰居，並選舉DR、BDR，所有非DR與DR、BDR建立Full鄰接關係，同步數據庫。