OSPF DR election configuration example

As shown in Figure 27:

• Enable OSPF on Switches A, B, C, and D on the same network.

• Configure Switch A as the DR, and configure Switch C as the BDR.

1. Configure IP addresses for interfaces. (Details not shown.)

2. Enable OSPF:

   # Configure Switch A.

   <SwitchA> system-view
   [SwitchA] router id 1.1.1.1
   [SwitchA] ospf
   [SwitchA-ospf-1] area 0
   [SwitchA-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
   [SwitchA-ospf-1-area-0.0.0.0] quit
   [SwitchA-ospf-1] quit
   

   # Configure Switch B.

   <SwitchB> system-view
   [SwitchB] router id 2.2.2.2
   [SwitchB] ospf
   [SwitchB-ospf-1] area 0
   [SwitchB-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
   [SwitchB-ospf-1-area-0.0.0.0] quit
   [SwitchB-ospf-1] quit
   

   # Configure Switch C.

   <SwitchC> system-view
   [SwitchC] router id 3.3.3.3
   [SwitchC] ospf
   [SwitchC-ospf-1] area 0
   [SwitchC-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
   [SwitchC-ospf-1-area-0.0.0.0] quit
   [SwitchC-ospf-1] quit
   

   # Configure Switch D.

   <SwitchD> system-view
   [SwitchD] router id 4.4.4.4
   [SwitchD] ospf
   [SwitchD-ospf-1] area 0
   [SwitchD-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
   [SwitchD-ospf-1-area-0.0.0.0] quit
   [SwitchD-ospf-1] return
   

   # Display OSPF neighbor information of Switch A.

   [SwitchA] display ospf peer verbose
   
             OSPF Process 1 with Router ID 1.1.1.1
                     Neighbors
   
    Area 0.0.0.0 interface 192.168.1.1(Vlan-interface1)'s neighbors
    Router ID: 2.2.2.2          Address: 192.168.1.2      GR State: Normal
      State: 2-Way  Mode: None  Priority: 1
      DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
      Options is 0x02 (-|-|-|-|-|-|E|-)
      Dead timer due in 38  sec
      Neighbor is up for 00:01:31
      Authentication Sequence: [ 0 ]
      BFD status: Disabled
   
    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
      Options is 0x02 (-|-|-|-|-|-|E|-)
      Dead timer due in 31  sec
      Neighbor is up for 00:01:28
      Authentication Sequence: [ 0 ]
      BFD status: Disabled
   
    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
      Options is 0x02 (-|-|-|-|-|-|E|-)
      Dead timer due in 31  sec
      Neighbor is up for 00:01:28
      Authentication Sequence: [ 0 ]
      BFD status: Disabled
   

   The output shows that Switch D is the DR and Switch C is the BDR.

3. Configure router priorities on interfaces:

   # Configure Switch A.

   [SwitchA] interface vlan-interface 1
   [SwitchA-Vlan-interface1] ospf dr-priority 100
   [SwitchA-Vlan-interface1] quit
   

   # Configure Switch B.

   [SwitchB] interface vlan-interface 1
   [SwitchB-Vlan-interface1] ospf dr-priority 0
   [SwitchB-Vlan-interface1] quit
   

   # Configure Switch C.

   [SwitchC] interface vlan-interface 1
   [SwitchC-Vlan-interface1] ospf dr-priority 2
   [SwitchC-Vlan-interface1] quit
   

   # Display neighbor information of Switch D.

   <SwitchD> display ospf peer verbose
   
             OSPF Process 1 with Router ID 4.4.4.4
                     Neighbors
   
    Area 0.0.0.0 interface 192.168.1.4(Vlan-interface1)'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
      Options is 0x02 (-|-|-|-|-|-|E|-)
      Dead timer due in 31  sec
      Neighbor is up for 00:11:17
      Authentication Sequence: [ 0 ]
      BFD status: Disabled
   
    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
      Options is 0x02 (-|-|-|-|-|-|E|-)
      Dead timer due in 35  sec
      Neighbor is up for 00:11:19
      Authentication Sequence: [ 0 ]
      BFD status: Disabled
   
    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
      Options is 0x02 (-|-|-|-|-|-|E|-)
      Dead timer due in 33  sec
      Neighbor is up for 00:11:15
      Authentication Sequence: [ 0 ]
      BFD status: Disabled
   

   The output shows that the DR and BDR are not changed, because the priority settings do not take effect immediately.

4. Restart OSPF process:

   # Restart the OSPF process of Switch D.

   <SwitchD> reset ospf 1 process
   Warning : Reset OSPF process? [Y/N]:y
   

   # Display neighbor information of Switch D.

   <SwitchD> display ospf peer verbose
   
             OSPF Process 1 with Router ID 4.4.4.4
                     Neighbors
   
    Area 0.0.0.0 interface 192.168.1.4(Vlan-interface1)'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
      Options is 0x02 (-|-|-|-|-|-|E|-)
      Dead timer due in 39  sec
      Neighbor is up for 00:01:40
      Authentication Sequence: [ 0 ]
      BFD status: Disabled
   
    Router ID: 2.2.2.2          Address: 192.168.1.2      GR State: Normal
      State: 2-Way  Mode: None  Priority: 0
      DR: 192.168.1.1  BDR: 192.168.1.3  MTU: 0
      Options is 0x02 (-|-|-|-|-|-|E|-)
      Dead timer due in 35  sec
      Neighbor is up for 00:01:44
      Authentication Sequence: [ 0 ]
      BFD status: Disabled
   
    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
      Options is 0x02 (-|-|-|-|-|-|E|-)
      Dead timer due in 39  sec
      Neighbor is up for 00:01:41
      Authentication Sequence: [ 0 ]
      BFD status: Disabled
   

   If the neighbor state is full, Switch D has established an adjacency with the neighbor. If the neighbor state is 2-way, the two switches are not the DR or the BDR, and they do not exchange LSAs.

   # Display OSPF interface information.

   [SwitchA] 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     Broadcast DR      1     100   192.168.1.1    192.168.1.3
   
   [SwitchB] 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
   

   The interface state DROther means the interface is not the DR or BDR.