配置 OSPF 的 DR 选择示例

组网需求

RouterA 的优先级为 100，它是网络上的最高优先级，所以 RouterA 被选为 DR；RouterC 是优先级第二高的，被选为 BDR；

RouterB 的优先级为 0，这意味着它将无法成为 DR 或 BDR； RouterD 没有配置优先级，取缺省值 1。

1、拓扑图

配置思路

OSPF 的 DR 选择：

1. 配置各路由器上 router id，使能 OSPF，指定网段。

2. 在缺省优先级情况下，查看各路由器 DR/BDR 状态。

3. 配置接口上的 DR 优先级，查看 DR/BDR 状态。

1. 配置各路由器上 router id，使能 OSPF，指定网段。 （本配置省略）

2. 在缺省优先级情况下，查看各路由器 DR/BDR 状态。

[AR1]dis ospf peer

	 OSPF Process 1 with Router ID 1.1.1.1
		 Neighbors

 Area 0.0.0.0 interface 192.168.1.1(GigabitEthernet0/0/0)'s neighbors
 Router ID: 2.2.2.2          Address: 192.168.1.2
   State: 2-Way  Mode:Nbr is  Master  Priority: 1
   DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 35  sec
   Retrans timer interval: 5
   Neighbor is up for 00:00:00
   Authentication Sequence: [ 0 ]

 Router ID: 3.3.3.3          Address: 192.168.1.3
   State: Full  Mode:Nbr is  Master  Priority: 1
   DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 39  sec
   Retrans timer interval: 5
   Neighbor is up for 00:05:48
   Authentication Sequence: [ 0 ]

 Router ID: 4.4.4.4          Address: 192.168.1.4
   State: Full  Mode:Nbr is  Master  Priority: 1
   DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 36  sec
   Retrans timer interval: 0
   Neighbor is up for 00:09:40
   Authentication Sequence: [ 0 ]

[AR1]

优先级相同时，router id 高的被选举为DR，第二高的选举为BDR.

D为DR,C为BDR.

3. 配置接口上的 DR 优先级，查看 DR/BDR 状态。

路由器A

[AR1]int g0/0/0
[AR1-GigabitEthernet0/0/0]ospf dr-priority 100
[AR1-GigabitEthernet0/0/0]quit

路由器B

[AR2]int g0/0/0
[AR2-GigabitEthernet0/0/0]ospf dr-priority 0

路由器C

[AR3]int g0/0/0
[AR3-GigabitEthernet0/0/0]ospf dr
[AR3-GigabitEthernet0/0/0]ospf dr-priority 2

重启OSPF进程，用户视图下：reset ospf 1 process

路由器A查看各节点身份

[AR1]dis ospf peer

	 OSPF Process 1 with Router ID 1.1.1.1
		 Neighbors

 Area 0.0.0.0 interface 192.168.1.1(GigabitEthernet0/0/0)'s neighbors
 Router ID: 2.2.2.2          Address: 192.168.1.2
   State: Full  Mode:Nbr is  Master  Priority: 0
   DR: 192.168.1.1  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 37  sec
   Retrans timer interval: 4
   Neighbor is up for 00:00:55
   Authentication Sequence: [ 0 ]

 Router ID: 3.3.3.3          Address: 192.168.1.3
   State: Full  Mode:Nbr is  Master  Priority: 2
   DR: 192.168.1.1  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 38  sec
   Retrans timer interval: 5
   Neighbor is up for 00:00:47
   Authentication Sequence: [ 0 ]

 Router ID: 4.4.4.4          Address: 192.168.1.4
   State: Full  Mode:Nbr is  Master  Priority: 1
   DR: 192.168.1.1  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 36  sec
   Retrans timer interval: 5
   Neighbor is up for 00:00:03
   Authentication Sequence: [ 0 ]

[AR1]

路由器A优先级为100的变成了DR,优先级为2的变成了BDR。优先级为0的不参与选举。

读书和健身总有一个在路上