组网需求
在下图中，RouterA的GE1/0/0接口的优先级为100，它是网络上的最高优先级，所以RouterA被选为DR；RouterC的GE1/0/0接口的优先级仅次于RouterA的GE1/0/0接口，被选为BDR；RouterB的优先级为0，这意味着它将不参加DR选举；RouterD没有配置优先级，取缺省值1。
控制OSPF的DR选择组网图
适用的产品和版本
路由器端可以使用任意一款NE产品，版本为(VRP5.30)及后续版本。
配置步骤
步骤 1 配置各接口的IP地址(略)
步骤 2 配置OSPF基本功能
# 配置RouterA。
[RouterA] router id 1.1.1.1
[RouterA] ospf
[RouterA-ospf-1] area 0
[RouterA-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
# 配置RouterB。
[RouterB] router id 2.2.2.2
[RouterB] ospf
[RouterB-ospf-1] area 0
[RouterB-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
# 配置RouterC。
[RouterC] router id 3.3.3.3
[RouterC] ospf
[RouterC-ospf-1] area 0
[RouterC-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
# 配置RouterD。
[RouterD] router id 4.4.4.4
[RouterD] ospf
[RouterD-ospf-1] area 0
[RouterD-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
# 查看DR/BDR的状态。
[RouterA]display ospf peer
OSPF Process 1 with Router ID 1.1.1.1
Neighbors
Area 0.0.0.0 interface 192.168.1.1(GigabitEthernet1/0/0)'s neighbors
Router ID: 2.2.2.2 Address: 192.168.1.2 GR State: Normal
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 32 sec
Neighbor is up for 00:04:21
Authentication Sequence: [ 0 ]
Router ID: 3.3.3.3 Address: 192.168.1.3 GR State: Normal
State: Full Mode:Nbr is Master Priority: 1
DR: 192.168.1.4 BDR: 192.168.1.3 MTU: 0
Dead timer due in 37 sec
Neighbor is up for 00:04:06
Authentication Sequence: [ 0 ]
Router ID: 4.4.4.4 Address: 192.168.1.4 GR State: Normal
State: Full Mode:Nbr is Master Priority: 1
DR: 192.168.1.4 BDR: 192.168.1.3 MTU: 0
Dead timer due in 37 sec
Neighbor is up for 00:03:53
Authentication Sequence: [ 0 ]
查看RouterA的邻居信息，可以看到DR优先级(缺省为1)以及邻居状态，此时RouterD为DR，RouterC为BDR。
说明
当优先级相同时，router-id高的为DR。如果路由器的某个Ethernet接口成为DR之后，则这台路由器的其他广播接口在进行后续的DR选择时，具有高优先权。即选择已经是DR的路由器作为DR，DR不可抢占。
步骤 3 配置接口上的DR优先级
# 配置RouterA。
[RouterA] interface GigabitEthernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ospf dr-priority 100
[RouterA-GigabitEthernet1/0/0] quit
# 配置RouterB。
[RouterB] interface GigabitEthernet 1/0/0
[RouterB-GigabitEthernet1/0/0] ospf dr-priority 0
[RouterB-GigabitEthernet1/0/0] quit
# 配置RouterC。
[RouterC] interface GigabitEthernet 1/0/0
[RouterC-GigabitEthernet1/0/0] ospf dr-priority 2
[RouterC-GigabitEthernet1/0/0] quit
# 查看DR/BDR的状态。
[RouterD]display ospf peer
OSPF Process 1 with Router ID 4.4.4.4
Neighbors
Area 0.0.0.0 interface 192.168.1.4(GigabitEthernet1/0/0)'s neighbors
Router ID: 1.1.1.1 Address: 192.168.1.1 GR State: Normal
State: Full Mode:Nbr is Slave Priority: 100
DR: 192.168.1.4 BDR: 192.168.1.3 MTU: 0
Dead timer due in 31 sec
Neighbor is up for 00:11:17
Authentication Sequence: [ 0 ]
Router ID: 2.2.2.2 Address: 192.168.1.2 GR State: Normal
State: Full Mode:Nbr is Slave Priority: 0
DR: 192.168.1.4 BDR: 192.168.1.3 MTU: 0
Dead timer due in 35 sec
Neighbor is up for 00:11:19
Authentication Sequence: [ 0 ]
Router ID: 3.3.3.3 Address: 192.168.1.3 GR State: Normal
State: Full Mode:Nbr is Slave Priority: 2
DR: 192.168.1.4 BDR: 192.168.1.3 MTU: 0
Dead timer due in 33 sec
Neighbor is up for 00:11:15
Authentication Sequence: [ 0 ]
说明
在接口上配置DR优先级之后并不会立即生效。
步骤 4 重启OSPF进程
在各路由器的用户视图下，同时执行命令reset ospf 1 process，以重启OSPF进程。
验证结果
# 查看OSPF邻居状态。
[RouterD] display ospf peer
OSPF Process 1 with Router ID 4.4.4.4
Neighbors
Area 0.0.0.0 interface 192.168.1.4(GigabitEthernet1/0/0)'s neighbors
Router ID: 1.1.1.1 Address: 192.168.1.1 GR State: Normal
State: Full Mode:Nbr is Slave Priority: 100
DR: 192.168.1.1 BDR: 192.168.1.3 MTU: 0
Dead timer due in 35 sec
Neighbor is up for 00:07:19
Authentication Sequence: [ 0 ]
Router ID: 2.2.2.2 Address: 192.168.1.2 GR State: Normal
State: 2-Way Mode:Nbr is Slave Priority: 0
DR: 192.168.1.1 BDR: 192.168.1.3 MTU: 0
Dead timer due in 35 sec
Neighbor is up for 00:07:19
Authentication Sequence: [ 0 ]
Router ID: 3.3.3.3 Address: 192.168.1.3 GR State: Normal
State: Full Mode:Nbr is Slave Priority: 2
DR: 192.168.1.1 BDR: 192.168.1.3 MTU: 0
Dead timer due in 37 sec
Neighbor is up for 00:07:17
Authentication Sequence: [ 0 ]
# 查看OSPF接口的状态。
[RouterA]display ospf interface
OSPF Process 1 with Router ID 1.1.1.1
Interfaces
Area: 0.0.0.0
IP Address Type State Cost Pri DR BDR
192.168.1.1 BroadcastDR 1 100 192.168.1.1 192.168.1.3
[RouterB]display ospf interface
OSPF Process 1 with Router ID 2.2.2.2
Interfaces
Area: 0.0.0.0
IP Address Type State Cost Pri DR BDR
192.168.1.2 Broadcast DROther 1 0 192.168.1.1 192.168.1.3
如果邻居的状态是Full，这说明它和邻居之间形成了邻接关系；如果停留在2-Way的状态，则说明他们都不是DR或BDR，两者之间不需要交换LSA。
如果OSPF接口的状态是DROther，则说明它既不是DR，也不是BDR。
配置文件
RouterA的配置文件
#
sysname RouterA
#
router id 1.1.1.1
#
interface GigabitEthernet1/0/0
ip address 192.168.1.1 255.255.255.0
ospf dr-priority 100
#
ospf 1
area 0.0.0.0
network 192.168.1.0 0.0.0.255
#
return
RouterB的配置文件
#
sysname RouterB
#
router id 2.2.2.2
#
interface GigabitEthernet1/0/0
ip address 192.168.1.2 255.255.255.0
ospf dr-priority 0
#
ospf 1
area 0.0.0.0
network 192.168.1.0 0.0.0.255
#
return
RouterC的配置文件
#
sysname RouterC
#
router id 3.3.3.3
#
interface GigabitEthernet1/0/0
ip address 192.168.1.3 255.255.255.0
ospf dr-priority 2
#
ospf 1
area 0.0.0.0
network 192.168.1.0 0.0.0.255
#
return
RouterD的配置文件
#
sysname RouterD
#
router id 4.4.4.4
#
interface GigabitEthernet1/0/0
ip address 192.168.1.4 255.255.255.0
#
ospf 1
area 0.0.0.0
network 192.168.1.0 0.0.0.255
#
return
