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How does OSPF select the router identification?



Article ID: KB8022 KB Last Updated: 12 Jan 2010Version: 3.0
OSPF selection of router-id on a Netscreen Firewall.
Explain how OSPF selects the router identification and the suggestions.
If you do not define a specific virtual router ID (VR ID) before enabling a dynamic routing protocol, ScreenOS automatically selects the highest IP address of the active interfaces in the virtual router (VR) for the router identifier.

The router identification must be unique on each routing device, or it will cause a problem with routing because there cannot be multiple security VRs with the same VR ID in a routing domain.

You can set the VR ID to the loopback interface address, as long as the loopback interface is not a Virtual Security Interface (VSI) in a NetScreen Redundancy Protocol (NSRP) cluster.

Although the firewall will assign the router-id automatically, it is strongly recommended to set the router id using the following command:

  set vr <vr-name> router-id <number>

You cannot assign or change a router ID if you have already enabled a dynamic routing protocol in the VR. If you need to change the router ID, you must first disable the dynamic routing protocol(s) in the VR.

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