How is the router ID for an OSPFv3 router determined?

In OSPFv3, the router ID is determined by selecting the highest IP address assigned to an active interface on the router. If no interfaces are available, OSPFv3 will use the highest IPv4 address among the router's loopback interfaces, if configured. If no loopback interfaces are present, and no active IP addresses are available, the router ID remains undefined until one is assigned or the router is restarted. The router ID is essential for uniquely identifying the OSPFv3 router within an OSPF network.