OSPF Configuration 255
The commands listed in the following examples enable Switch A and Switch C to be
DR and BDR, respectively. The priority of Switch A is 100, which is the highest on the
network, so it is elected as the DR. Switch C has the second highest priority, so it is
elected as the BDR. The priority of Switch B is 0, which means that it cannot be
elected as the DR, and Switch D does not have a priority, and therefore takes priority
1 by default.
Configuration Procedure
1 Configure Switch A:
[Switch A]interface Vlan-interface 1
[Switch A-Vlan-interface1]ip address 196.1.1.1 255.255.255.0
[Switch A-Vlan-interface1]ospf dr-priority 100
[Switch A]router id 1.1.1.1
[Switch A]ospf
[Switch A-ospf-1]area 0
[Switch A-ospf-1-area-0.0.0.0]network 196.1.1.0 0.0.0.255
2 Configure Switch B:
[Switch B]interface Vlan-interface 1
[Switch B-Vlan-interface1]ip address 196.1.1.2 255.255.255.0
[Switch B-Vlan-interface1]ospf dr-priority 0
[Switch B]router id 2.2.2.2
[Switch B]ospf
[Switch B-ospf-1]area 0
[Switch B-ospf-1-area-0.0.0.0]network 196.1.1.0 0.0.0.255
3 Configure Switch C:
[Switch C]interface Vlan-interface 1
[Switch C-Vlan-interface1]ip address 196.1.1.3 255.255.255.0
[Switch C-Vlan-interface1]ospf dr-priority 2
[Switch C]router id 3.3.3.3
[Switch C]ospf
[Switch C-ospf-1]area 0
[Switch C-ospf-1-area-0.0.0.0]network 196.1.1.0 0.0.0.255
4 Configure Switch D:
[Switch D]interface Vlan-interface 1
[Switch D-Vlan-interface1]ip address 196.1.1.4 255.255.255.0
[Switch D]router id 4.4.4.4
[Switch D]ospf
[Switch D-ospf-1]area 0
[Switch D-ospf-1-area-0.0.0.0]network 196.1.1.0 0.0.0.255
On Switch A, run the display ospf peer command to show the Switch’s OSPF
neighbors. Note that Switch A has three neighbors.
The status of each neighbor is full, which means that adjacency is set up between
Switch A and each neighbor. Switch A and Switch C should be set up with
adjacencies to all the routers on the network so that they can serve as the DR and
BDR on the network. Switch A is DR, while Switch C is BDR on the network. All the
other neighbors are DROthers (which means that they are neither DRs nor BDRs).
5 Modify the priority of Switch B to 200:
[Switch B-Vlan-interface2000]ospf dr-priority 200
Execute the display ospf peer command on Switch A to show its OSPF neighbors.
Please note the priority of Switch B has been modified to 200, but it is still not the DR.
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