一、实验拓扑：
二、命令部署：
略
三、验证：
R3#show ip ospf neighbor 查看DR、BDR
R1#clear ip ospf process 清除OSPF进程
R1(config)#int f0/0 R1(config-if)#ip ospf priority 10 修改优先级
注意：增加R6，如果把200.1.1.6通告进入area 0，那么R6就是新的DR； 如果通告进area 1，那么R6是200.1.1.0的DR，R5是200.1.1.0的BDR； 这样结果，R5既是DR又是BDR，只不过在不同的网段。
1、验证：重启后/清除进程后 R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 2.2.2.2 1 2WAY/DROTHER 00:00:32 100.1.1.2 FastEthernet0/0 3.3.3.3 1 2WAY/DROTHER 00:00:32 100.1.1.3 FastEthernet0/0 4.4.4.4 1 FULL/BDR 00:00:34 100.1.1.4 FastEthernet0/0 5.5.5.5 1 FULL/DR 00:00:35 100.1.1.5 FastEthernet0/0 2、验证：R1增加优先级重启后 R2#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface 1.1.1.1 10 FULL/DR 00:00:36 100.1.1.1 FastEthernet0/0 3.3.3.3 1 2WAY/DROTHER 00:00:36 100.1.1.3 FastEthernet0/0 4.4.4.4 1 2WAY/DROTHER 00:00:36 100.1.1.4 FastEthernet0/0 5.5.5.5 1 FULL/BDR
R1(config)#int f0/0 R1(config-if)#shutdown R2#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 1 2WAY/DROTHER 00:00:30 100.1.1.3 FastEthernet0/0 4.4.4.4 1 FULL/BDR 00:00:34 100.1.1.4 FastEthernet0/0 5.5.5.5 1 FULL/DR 00:00:34 100.1.1.5 FastEthernet0/0 3、R3、R4把优先级改为0后 R4(config)#int f0/0 R4(config-if)#ip ospf priority 0 R3(config)#int f0/0 R3(config-if)#ip ospf priority 0
R2#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 0 FULL/DROTHER 00:00:34 100.1.1.3 FastEthernet0/0 4.4.4.4 0 FULL/DROTHER 00:00:35 100.1.1.4 FastEthernet0/0 5.5.5.5 1 FULL/DR 4、增加R6后： R2#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 0 FULL/DROTHER 00:00:38 100.1.1.3 FastEthernet0/0 4.4.4.4 0 FULL/DROTHER 00:00:38 100.1.1.4 FastEthernet0/0 5.5.5.5 1 FULL/DR 00:00:39 100.1.1.5 FastEthernet0/0
R6#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface 5.5.5.5 1 FULL/BDR 00:00:34 200.1.1.5 FastEthernet0/0
