What happens when a router receives an OSPF Hello packet but its own router ID is not included?

When a router receives an OSPF Hello packet that does not contain its own router ID, it will transition to the Init state. This indicates that the router has received a Hello packet from a neighboring router, but the neighbor is not yet fully aware of the router's presence in that area.

In OSPF, the Hello protocol is used to establish and maintain neighbor relationships among routers. The router uses the Hello packets to discover neighbors and to maintain those relationships. When a router sends a Hello packet, it lists the router IDs of all routers that it recognizes as its neighbors.

The Init state signifies that while the router has detected a neighbor, it has not yet established a complete communication link with that neighbor, as its own router ID is missing from the received Hello packet. Consequently, this state is crucial for the router to identify which of its neighbors are acknowledged and which ones may still need to be recognized in order to form a fully functional adjacence.