Configuring OSPF Auto Cost Reference Bandwidth

A single autonomous system’s routers communicate with one another using the routing protocol OSPF, or Open Shortest Path First, using link state technology (AS). Higher bandwidth links are favoured over lower bandwidth lines according to the OSPF cost metric, which is dependent on link bandwidth. To make sure that the quickest path is always chosen, the cost metric must be changed because not all network interfaces have the same capacity.

Configuring OSPF Auto Cost Reference Bandwidth, the reference bandwidth used to generate the OSPF cost measure, is one way to change it. The OSPF Auto Cost Reference Bandwidth’s default setting of 100 Mbps can be increased to ensure that greater bandwidth links are prioritised.

Steps for OSPF Auto Cost Reference Bandwidth Configuration 

Step 1: Enter the router configuration mode. You must enter the router configuration mode to configure the OSPF Auto Cost Reference Bandwidth. This can be accomplished by going to the router’s administrative page by putting the router’s IP address into a web browser.

Step 2: Activate OSPF, before configuring the Auto Cost Reference Bandwidth, OSPF must be configured on the router. Enter the router ospf process-id command in the router configuration mode to enable OSPF.

Step 3: The OSPF Auto Cost Reference Bandwidth should be set to, and enter the auto-cost reference-bandwidth bandwidth command in the router configuration mode to specify the OSPF Auto Cost Reference Bandwidth. Put the required reference bandwidth in place of “bandwidth”. For instance, you would type “auto-cost reference-bandwidth 1000” to set the reference bandwidth to 1 Gbps.

Step 4: After setting up the OSPF Auto Cost Reference Bandwidth, check the configuration to make sure it was implemented properly. You can do this by executing the command display ip ospf interface in the router configuration mode.

This command’s output will include details about the OSPF interface, including the specified reference bandwidth. The same command can be used to confirm the OSPF cost metric for each interface.

The reference bandwidth is used by OSPF (Open Shortest Path First) to compute a link’s cost, which is then used to identify the shortest path to a destination. The reference bandwidth is 100Mbps by default. The OSPF Auto Cost Reference Bandwidth configuration, however, allows you to alter this number. Here is how you do it:

1. Use the CLI of the router (command-line interface).
2. By entering the following command, global configuration mode will be activated:

config ter

3. Switch to OSPF configuration mode.

Router(config)# router ospf <process id>

4. By entering the following command, the OSPF Auto Cost Reference Bandwidth will be set:

Router(config-router)# auto-cost reference-bandwidth bandwidth-in-mbps

5. Substitute “bandwidth-in-mbps” with the desired number for the reference bandwidth. For instance, you might type: to set the reference bandwidth to 1 Gbps.

Router(config-router)#  auto Cost Reference Bandwidth 1000

6. Type exit to leave global configuration mode.

7. Type: to save your configuration.

Router# copy run start 

8. You have now chosen the desired value for your OSPF Auto Cost Reference Bandwidth. This value will be used to compute the cost of a link when OSPF is functioning on your network.