What is the format of the router ID on an OSPF-enabled router?

The router ID on an OSPF-enabled router is expressed as a 32-bit number formatted like an IPv4 address. This format allows the router to have a unique identifier within an OSPF routing domain. The router ID serves as a critical element in OSPF since it is used to identify the router in OSPF messages and in the OSPF database.

Using a format akin to an IPv4 address makes it easier for network administrators to recognize and manage the router IDs because they can relate them to familiar IP addressing schemes. Each router selects its router ID from one of its IP addresses, and if there are no loopback interfaces configured, it will typically choose the highest IP address assigned to any of its active interfaces.

This format is also significant because OSPF relies on these identifiers to establish neighbor relationships and to manage routing tables effectively. Therefore, the choice of a 32-bit number formatted like an IPv4 address is integral to the proper functioning of OSPF.