Which OSPF state follows after the router has received valid Hello packets?

In the OSPF (Open Shortest Path First) protocol, the communication process between routers begins with the exchange of Hello packets. When a router receives valid Hello packets from another router, it transitions to the 2-way state. This state signifies that bi-directional communication has been established between neighbors, meaning both routers have acknowledged each other's existence.

In the 2-way state, routers have exchanged their Router ID and other OSPF interface information through Hello packets. This state is significant because it allows routers to recognize which neighbors they can form adjacencies with. Only routers that are in the 2-way state can proceed to the next stages of the OSPF process, such as the Exchange state, where they start sharing link-state information, which is critical for building the OSPF routing table.

Understanding this progression is vital for grasping how OSPF forms and maintains its neighbor relationships and overall network topology.