Example for Configuring OSPF DR Election

This section describes how to set the DR priority on an interface for DR election on a broadcast network.

Networking Requirements

On the network shown in Figure 1, the interface of Device A has the highest priority of 100 on the network and is elected as the DR; Device C has the second highest priority and is elected as the BDR. Device B has the priority of 0 and cannot be elected as a DR or a BDR; no priority is configured for Device D and therefore, Device D uses the default value (1).

Figure 1 Networking for configuring OSPF DR election

Interface 1 in this example represents GE 0/1/0.

Precautions

Reconfiguring the DR priority for a router does not change the DR or BDR on a network. You can use either of the following methods to re-elect a DR or BDR. However, the following methods will disconnect OSPF neighbors. Therefore, use the following methods only when necessary.

Restart the OSPF processes on all routers.
Configure the shutdown and undo shutdown commands on the interfaces where the OSPF neighboring relationships are established.

Configuration Roadmap

The configuration roadmap is as follows:

Configure basic OSPF functions on each router for interconnection.
Configure the Router ID for each router.
Use the default DR priorities and check whether the router is the DR or BDR.
Configure the DR priority on an interface and check whether the device is the DR or BDR.

Data Preparation

To complete the configuration, you need the following data:

Router ID (1.1.1.1) and priority (100) of Device A
Router ID (2.2.2.2) and priority (0) of Device B
Router ID (3.3.3.3) and priority (2) of Device C
Router ID (4.4.4.4) and priority (1) of Device D

Procedure

Assign an IP address to each interface. For configuration details, see Configuration Files in this section.

Configure basic OSPF functions.

# Configure DeviceA.

<HUAWEI> system-view
[~DeviceA] router id 1.1.1.1
[~DeviceA] ospf 1
[*DeviceA-ospf-1] area 0
[*DeviceA-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
[*DeviceA-ospf-1-area-0.0.0.0] commit
[~DeviceA-ospf-1-area-0.0.0.0] quit

# Configure DeviceB.

<HUAWEI> system-view
[~DeviceB] router id 2.2.2.2
[~DeviceB] ospf 1
[*DeviceB-ospf-1] area 0
[*DeviceB-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255 
[*DeviceB-ospf-1-area-0.0.0.0] commit
[~DeviceB-ospf-1-area-0.0.0.0] quit

# Configure DeviceC.

<HUAWEI> system-view
[~DeviceC] router id 3.3.3.3
[~DeviceC] ospf 1
[*DeviceC-ospf-1] area 0
[*DeviceC-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
[*DeviceC-ospf-1-area-0.0.0.0] commit
[~DeviceC-ospf-1-area-0.0.0.0] quit

# Configure DeviceD.

<HUAWEI> system-view
[~DeviceD] router id 4.4.4.4
[~DeviceD] ospf 1
[*DeviceD-ospf-1] area 0
[*DeviceD-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255 
[*DeviceD-ospf-1-area-0.0.0.0] commit
[~DeviceD-ospf-1-area-0.0.0.0] quit

# Display the status of the DR or BDR.

[~DeviceA] display ospf peer
          OSPF Process 1 with Router ID 1.1.1.1
                Neighbors

 Area 0.0.0.0 interface 192.168.1.1 ( GE0/1/0 )'s neighbors
 Router ID: 2.2.2.2         Address: 192.168.1.2
   State: 2-Way  Mode:Nbr is  Slave   Priority: 1
   DR: 192.168.1.4   BDR: 192.168.1.3    MTU: 0
   Dead timer due in  32  sec
   Retrans timer interval: 0
   Neighbor is up for 1h15m4s
   Neighbor up time : 2020-06-08 01:41:57
   Authentication Sequence: [ 0 ]

 Area 0.0.0.0 interface 192.168.1.1 ( GE0/1/0 )'s neighbors
 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  34  sec
   Retrans timer interval: 5
   Neighbor is up for 1h15m4s
   Neighbor up time : 2020-06-08 01:41:57
   Authentication Sequence: [ 0 ]

 Area 0.0.0.0 interface 192.168.1.1 ( GE0/1/0 )'s neighbors
 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  32  sec
   Retrans timer interval: 5
   Neighbor is up for 1h15m4s
   Neighbor up time : 2020-06-08 01:41:57
   Authentication Sequence: [ 0 ]

Check the neighbor information of DeviceA. You can view the DR priority and the neighbor status. By default, the DR priority is 1. Now DeviceD functions as the DR and DeviceC functions as the BDR.

Set the DR priority on each interface.

# Configure Device A.

[~DeviceA] interface gigabitethernet 0/1/0
[~DeviceA-GigabitEthernet0/1/0] ospf dr-priority 100
[*DeviceA-GigabitEthernet0/1/0] commit
[~DeviceA-GigabitEthernet0/1/0] quit

# Configure Device B.

[~DeviceB] interface gigabitethernet 0/1/0
[~DeviceB-GigabitEthernet0/1/0] ospf dr-priority 0
[*DeviceB-GigabitEthernet0/1/0] commit
[~DeviceB-GigabitEthernet0/1/0] quit

# Configure Device C.

[~DeviceC] interface gigabitethernet 0/1/0
[~DeviceC-GigabitEthernet0/1/0] ospf dr-priority 2
[*DeviceC-GigabitEthernet0/1/0] commit
[~DeviceC-GigabitEthernet0/1/0] quit

# Display the status of the DR or BDR.

[~DeviceD] display ospf peer
          OSPF Process 1 with Router ID 4.4.4.4
                Neighbors

 Area 0.0.0.0 interface 192.168.1.4 ( GE0/1/0 )'s neighbors
 Router 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  38  sec
   Retrans timer interval: 5
   Neighbor is up for 2h15m4s
   Neighbor up time : 2020-06-08 01:41:57
   Authentication Sequence: [ 0 ]

 Area 0.0.0.0 interface 192.168.1.4 ( GE0/1/0 )'s neighbors
 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  38  sec
   Retrans timer interval: 5
   Neighbor is up for 2h15m4s
   Neighbor up time : 2020-06-08 01:41:57
   Authentication Sequence: [ 0 ]

 Area 0.0.0.0 interface 192.168.1.4 ( GE0/1/0 )'s neighbors
 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  30  sec
   Retrans timer interval: 5
   Neighbor is up for 2h15m4s
   Neighbor up time : 2020-06-08 01:41:57
   Authentication Sequence: [ 0 ]

Restart the OSPF processes.
In the user view of each router, run the reset ospf 1 process command to restart the OSPF process.

Verify the configuration.

# Display the status of OSPF neighbors.

[~DeviceD] display ospf peer
          OSPF Process 1 with Router ID 4.4.4.4
                Neighbors

 Area 0.0.0.0 interface 192.168.1.4 ( GE0/1/0 )'s neighbors
 Router 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 3h15m4s
   Neighbor up time : 2020-06-08 01:41:57
   Authentication Sequence: [ 0 ]

 Area 0.0.0.0 interface 192.168.1.4 ( GE0/1/0 )'s neighbors
 Router ID: 2.2.2.2         Address: 192.168.1.2
   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
   Retrans timer interval: 0
   Neighbor is up for 3h15m4s
   Neighbor up time : 2020-06-08 01:41:57
   Authentication Sequence: [ 0 ]

 Area 0.0.0.0 interface 192.168.1.4 ( GE0/1/0 )'s neighbors
 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 3h15m4s
   Neighbor up time : 2020-06-08 01:41:57
   Authentication Sequence: [ 0 ]

# Display the status of OSPF interfaces.

[~DeviceA] display ospf interface
2020-11-21 15:55:20.606

(M) Indicates MADJ interface
          OSPF Process 1 with Router ID 1.1.1.1
                  Interfaces
                  
 Area: 0.0.0.0    (MPLS TE not enabled)
 Interface              IP Address     Type         State    Cost    Pri
 GigabitEthernet0/1/0   192.168.1.1    Broadcast    DR       1       100
[~DeviceB] display ospf interface
2020-11-21 15:55:20.606

(M) Indicates MADJ interface

          OSPF Process 1 with Router ID 2.2.2.2
                  Interfaces
                  
 Area: 0.0.0.0    (MPLS TE not enabled)
 Interface              IP Address     Type         State      Cost     Pri
 GigabitEthernet0/1/0   192.168.1.2    Broadcast    DROther    1        100

If the neighbor is in the Full state, the device has established a neighbor relationship with its neighbor. If the neighbor remains in the 2-Way state, neither of them is the DR or BDR. In this case, they do not need to exchange LSAs.

If the status of the OSPF interface is DROther, the interface is neither DR nor BDR.

Configuration Files

Device A configuration file

#
 sysname DeviceA
#
router id 1.1.1.1
#
interface GigabitEthernet0/1/0
 undo shutdown
 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

Device B configuration file

#
 sysname DeviceB
#
router id 2.2.2.2
#
interface GigabitEthernet0/1/0
 undo shutdown
 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

Device C configuration file

#
 sysname DeviceC
#
router id 3.3.3.3
#
interface GigabitEthernet0/1/0
 undo shutdown
 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

Device D configuration file

#
 sysname DeviceD
#
router id 4.4.4.4
#
interface GigabitEthernet0/1/0
 undo shutdown
 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