Router ID - OSPF

There are three methods of choosing Router ID (Same concept in all protocols)

1. Hard coded Router ID (Enforce router to adopt hard coated router ID).
2. Highest IP address of any logical (Virtual) interface will be router ID even if physical interface has the highest IP address.
3. The highest IP address on any physical interface (when there’s no virtual interface)

§  Never use a physical interface’s IP or Logical interface IP as your router ID always use hard coded Router ID.

A(config-router)# router-id 1.1.1.1

§  Router ID is command of new IOS it’s not supported in old IOS versions.

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