OSPF router ID in an IPv6 environment
An OSPF router ID must be assigned to an OSPF router in order for it to operate correctly. An OSPF router ID is always in the form of an IPv4 address. In an exclusively IPv6 environment, an OSPF router will be unable to automatically choose a router ID. For this reason, in such an environment, in order for an OSPF router to obtain a router ID, you must either:
- manually configure it
- configure a loopback interface with an IPv4 address
- configure an active physical interface with an IPv4 address.
Best practice dictates that you should manually configure the router ID.
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