Example for Configuring DR Election of OSPF
Networking Requirements
As shown in Figure 5-37, Router A has the highest priority (100) in the network and is elected as the DR. Router C has the second highest priority, and is elected as the BDR. The priority of Router B is 0, and Router B cannot be elected as the DR or BDR. The priority of Router D is not configured and its default value is 1.
Configuration Roadmap
The configuration roadmap is as follows:
Configure the router ID on each router, enable OSPF, and specify the network segment.
Check the DR/BDR status of each router with the default priority.
Configure the DR priority of the interface and check the DR/BDR status.
Procedure
- Configure an IP address for each interface.
# Configure IP addresses for all interfaces of RouterA.
<Huawei> system-view [Huawei] sysname RouterA [RouterA] interface gigabitethernet 1/0/0 [RouterA-GigabitEthernet1/0/0] ip address 192.168.1.1 255.255.255.0 [RouterA-GigabitEthernet1/0/0] quit
The configurations of RouterB, RouterC and RouterD are similar to the configuration of RouterA, and are not mentioned here.
- Configure basic OSPF functions.
# Configure Router A.
[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[RouterA-ospf-1-area-0.0.0.0] quit[RouterA-ospf-1] quit# Configure Router B.
[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[RouterB-ospf-1-area-0.0.0.0] quit[RouterB-ospf-1] quit# Configure Router C.
[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[RouterC-ospf-1-area-0.0.0.0] quit[RouterC-ospf-1] quit# Configure Router D.
[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[RouterD-ospf-1-area-0.0.0.0] quit[RouterD-ospf-1] quit# View the DR/BDR status.
[RouterA] display ospf peerOSPF Process 1 with Router ID 1.1.1.1
Neighbors
Area 0.0.0.0 interface 192.168.1.1(GigabitEthernet1/0/0)'s neighborsRouter 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 32 sec
Retrans timer interval: 5
Neighbor is up for 00:04:21
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 37 sec
Retrans timer interval: 5
Neighbor is up for 00:04:06
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 37 sec
Retrans timer interval: 5
Neighbor is up for 00:03:53
Authentication Sequence: [ 0 ]
# View the neighbor information of Router A. You can see the priority of DR and the neighbor status. The Router D is the DR, and Router C is the BDR.
When the priority is the same, the router with a higher router ID is elected as the DR. If a new router is added after the DR/BDR election is complete, the new router cannot become the DR even if it has the highest priority.
- Configure DR priorities on interfaces.
# Configure Router A.
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ospf dr-priority 100
[RouterA-GigabitEthernet1/0/0] quit
# Configure Router B.
[RouterB] interface gigabitethernet 1/0/0
[RouterB-GigabitEthernet1/0/0] ospf dr-priority 0
[RouterB-GigabitEthernet1/0/0] quit
# Configure Router C.
[RouterC] interface gigabitethernet 1/0/0
[RouterC-GigabitEthernet1/0/0] ospf dr-priority 2
[RouterC-GigabitEthernet1/0/0] quit
# View the DR/BDR status.
[RouterD] display ospf peerOSPF Process 1 with Router ID 4.4.4.4
Neighbors
Area 0.0.0.0 interface 192.168.1.4(GigabitEthernet1/0/0)'s neighborsRouter ID: 1.1.1.1 Address: 192.168.1.1
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
Retrans timer interval: 5
Neighbor is up for 00:11:17
Authentication Sequence: [ 0 ]
Router ID: 2.2.2.2 Address: 192.168.1.2
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
Retrans timer interval: 5
Neighbor is up for 00:11:19
Authentication Sequence: [ 0 ]
Router ID: 3.3.3.3 Address: 192.168.1.3
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
Retrans timer interval: 5
Neighbor is up for 00:11:15
Authentication Sequence: [ 0 ]
- Restart OSPF processes.
In the user view of each router, run the reset ospf 1 process command to restart the OSPF process.
- View the configuration.
# View the status of OSPF neighbors.
[RouterD] display ospf peerOSPF Process 1 with Router ID 4.4.4.4
Neighbors
Area 0.0.0.0 interface 192.168.1.4(GigabitEthernet1/0/0)'s neighborsRouter ID: 1.1.1.1 Address: 192.168.1.1
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
Retrans timer interval: 5
Neighbor is up for 00:07:19
Authentication Sequence: [ 0 ]
Router ID: 2.2.2.2 Address: 192.168.1.2
State: 2-Way Mode:Nbr is Master Priority: 0
DR: 192.168.1.1 BDR: 192.168.1.3 MTU: 0
Dead timer due in 35 sec
Retrans timer interval: 5
Neighbor is up for 00:07:19
Authentication Sequence: [ 0 ]
Router ID: 3.3.3.3 Address: 192.168.1.3
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
Retrans timer interval: 5
Neighbor is up for 00:07:17
Authentication Sequence: [ 0 ]
# View the status of the OSPF interface.
[RouterA] display ospf interfaceOSPF 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 Broadcast DR 1 100 192.168.1.1 192.168.1.3
[RouterB] display ospf interfaceOSPF 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
If all neighbors are in the Full state, it indicates that Router A establishes the neighbor relationship with its neighbor. If the neighbor stays "2-Way", it indicates both of them are not the DR or BDR. They need not exchange LSAs.
If the status of the OSPF interface is DROther, it indicates that it is neither DR nor BDR.
Configuration Files
Configuration file of Router A
#
sysname RouterA#
router id 1.1.1.1
#
interface GigabitEthernet1/0/0ip 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
Configuration file of Router B
#
sysname RouterB#
router id 2.2.2.2
#
interface GigabitEthernet1/0/0ip 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
Configuration file of Router C
#
sysname RouterC#
router id 3.3.3.3
#
interface GigabitEthernet1/0/0ip 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
Configuration file of Router D
#
sysname RouterD#
router id 4.4.4.4
#
interface GigabitEthernet1/0/0ip 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
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