Lab 6.2.3 Controlling a DR/BDR Election
Step 1: Connect the equipment
Connect each of the router Fa0/0 interfaces to any port on the switch using a straight-through cable.
Step 2: Perform basic configuration on the routers.
- Connect a PC to the console port of the router to perform configurations using a terminal emulation program.
- Configure Routers 1, 2, and 3 with a hostname, and console, Telnet, and privileged passwords according to the table diagram.
Step 3: Configure single area OSPF routing on the routers
Configure basic OSPF routing on the routers. All networks are in Area 0.
Step 4: Verify current OSPF operation
- Now that the Ethernet interfaces and OSPF have been configured, OSPF should be operational between the routers. Because this is a multi-access network, a DR/BDR election should have occurred.
- Use the show ip ospf neighbor command on all the routers to verify operation. The output should be similar to what is shown below.
Step 5: Configure router loopback interfaces
- Configuring loopback interfaces for OSPF operation serves two purposes: 1) Because loopback interfaces are logical interfaces and never go down, it ensures that the router ID will never change. 2) Configuring loopback interfaces allows control over the DR/BDR election.
- Configure the loopback interfaces as shown in the addressing table on the first page.
- Use the show ip ospf neighbor detail command on R1 to view the DR/BDR status. Have the DR and BDR routers changed? __________ No
- Once elected, the DR and the BDR do not change unless the interfaces all cycle or the OSPF processes are reset. Use the clear ip ospf 1 process command on all routers to reset the OSPF processes.
- After the processes have been reset, use the show ip ospf neighbor detail command to recheck the DR/BDR status.
Step 6: Use router interface priority to determine DR election
- Another method that is used to determine the DR/BDR election is router interface priority. Use the show ip ospf interface command to determine the default priority settings on the routers.
- Configure interface priorities on R1 and R2 to determine the DR/BDR election results.
- Use the show ip ospf neighbor command to determine the DR and BDR. Have the DR and the BDR changed? __________ No
- Use the clear ip ospf 1 process command on all of the routers to reset the OSPF processes.
Step 7: Reflection
List the criteria used from highest to lowest for determining the DR on an OSPF network. Jawaban: Highest is interface priority. Next is highest router ID which is determined by the highest loopback address, or in the event of no loopbacks being configured, it is the highest active interface address.
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