In the OSPF (Open Shortest Path First) protocol used by MikroTik routers, the router-id is a unique identifier used to distinguish a router within an OSPF area.

This ID is crucial to the operation of the OSPF protocol, as it ensures that each router has a unique identification within the OSPF network.

We explain how it is determined and how you can obtain or configure the router-id on a MikroTik router:

How the Router-ID is Determined

1. Manual Assignment: The safest way to set a router-id is to assign it manually in the OSPF configuration. This ensures that the ID is unique and constant, which is important for the stability of the OSPF network.
2. Automatically by the System: If a router-id is not assigned manually, the MikroTik router will automatically select the router-id based on the IP addresses of its interfaces. Typically, it chooses the highest IP address configured on the router interfaces. If the IP addresses change, the automatic router-id could also change, which could potentially lead to stability issues in the OSPF network.

How to Get the Router-ID

To verify the current router-id on a MikroTik router, you can do it through the terminal or WinBox:

• By Terminal:
  • Access the terminal of your MikroTik router.
  • Enter the command /routing ospf instance print. This will show you the configuration of the OSPF instance, including the router-id.
• By WinBox:
  • Open WinBox and connect to your MikroTik router.
  • Go to “Routing” -> “OSPF” -> “Instances”. Here you can see the configured OSPF instances and their respective router-ids.

How to Manually Configure the Router-ID

To manually set a router-id on an OSPF instance:

1. By Terminal:
   • Use the command /routing ospf instance set [number] router-id=[desired-router-id]Where [number] is the OSPF instance number and [desired-router-id] is the ID you want to assign.
2. By WinBox:
   • Go to “Routing” -> “OSPF” -> “Instances”.
   • Select the instance you want to modify and click “Edit”.
   • In the “Router ID” field, enter the ID you want to assign and save the changes.

Assigning a router-id manually is a good practice in OSPF networks to avoid identification problems that could arise if the router automatically selects the ID based on the IP addresses of the interfaces, especially in networks that experience IP configuration changes.