CCNA3 - Lab 6.2.4 Part B: Configuring and Verifying Multi-access OSPF

Step 1: Connect the equipment

Connect the Fa0/0 interface of each router to the switch using a straight-through cable. Three routers are sharing a common Ethernet multi-access network, 192.168.1.0/24. Each router will be configured with an IP address on the FastEthernet interface and a loopback address for the router ID.

Step 2: Perform basic configurations on the routers

Step 3: Configure and activate Ethernet and Loopback addresses

Step 4: Verify IP addressing and interfaces

1. Use the show ip interface brief or the show protocols command to verify that the IP addressing is correct and that the interfaces are active.
2. After all interfaces are verified, be sure to save the running configuration to the NVRAM of the router.

Step 5: Configure OSPF on the DR router

The DR and BDR election process takes place as soon as the first router has its interface enabled for OSPF on the multi-access network. If OSPF is already configured for an interface, this can happen as the routers are powered on.

Step 6: Configure OSPF on the BDR router

1. Configure the OSPF process on the router with the second highest router ID to ensure that this router becomes the BDR. Use the router ospf command in global configuration mode to enable OSPF on the R2 router. What console message was displayed as a result of the OSPF commands on R2 and what does this mean? Jawaban: An OSPF adjacency message displayed indicating an adjacency was formed with the R3 router (Nbr 192,168.31.33). When the hello packet is received, the neighbor relationship is formed.

00:08:51: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.31.33 on

FastEthernet0/0 from LOADING to FULL, Loading Done

1. Use the show ip ospf interface command to verify that the OSPF has been configured correctly and that R2 is the BDR.

Step 7: Configure OSPF on the DRother router

1. Configure the OSPF process on the router with the lowest router ID last. This router will be designated as DRother instead of DR or BDR. Use the router ospf command in global configuration mode to enable OSPF on the R1 router
2. Use the show ip ospf interface command to verify that the OSPF has been configured correctly and that R1 is a DRother.

Step 8: Use the OSPF priority to determine the DR and BDR

1. Use the ip ospf priority interface command to change the OSPF priority of the R1 router to 255. This is the highest possible priority.
2. Use the ip ospf priority interface command to change the OSPF priority of the R3 router to 100.
3. Use the ip ospf priority interface command to change the OSPF priority of the R2 router to 0. A priority of 0 causes the router to be ineligible to participate in an OSPF election and become a DR or BDR.
4. Shut down and re-enable the FastEthernet0/0 interfaces to force an OSPF election. As the interfaces are shut down, the OSPF adjacencies are lost.

Step 9: Reflection

1. When the OSPF process starts, what happens if there is no active interface on the router? Jawaban: OSPF will not start.
2. What can be done to ensure there will be an active interface on a router? Jawaban: Configure a loopback interface.
3. How are the DR and BDR elected in an OSPF network? Jawaban: The DR is chosen with the highest OSPF priority value. The BDR is chosen with the second highest priority value. If the priority is the same, the OSPF election for DR is decided on the highest Router ID.
4. What OSPF interface priority value prevents a router from being elected as a DR? jawaban: 0