配置 OSPF 的 DR 選擇示例

阿新 • • 發佈：2020-09-15

組網需求

RouterA 的優先順序為 100，它是網路上的最高優先順序，所以 RouterA 被選為 DR；RouterC 是優先順序第二高的，被選為 BDR；
RouterB 的優先順序為 0，這意味著它將無法成為 DR 或 BDR； RouterD 沒有配置優先順序，取預設值 1。

1、拓撲圖

配置思路

OSPF 的 DR 選擇：

1. 配置各路由器上 router id，使能 OSPF，指定網段。
2. 在預設優先順序情況下，檢視各路由器 DR/BDR 狀態。
3. 配置介面上的 DR 優先順序，檢視 DR/BDR 狀態。

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

2. 在預設優先順序情況下，檢視各路由器 DR/BDR 狀態。

[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]

優先順序相同時，router id 高的被選舉為DR，第二高的選舉為BDR.

D為DR,C為BDR.

3. 配置介面上的 DR 優先順序，檢視 DR/BDR 狀態。

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

重啟OSPF程序，使用者檢視下：reset ospf 1 process

路由器A檢視各節點身份

[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優先順序為100的變成了DR,優先順序為2的變成了BDR。優先順序為0的不參與選舉。

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