OSPF Operational States
Two-Way State
In this state, communication between the two routers is bidirectional. On multiaccess links, the routers elect a DR and a BDR. Transition to ExStart state.
Full State
The link-state database of the router is fully synchronized.
Init State
Hello packets are received from the neighbor. They contain the Router ID of the sending router. Transition to Two-Way state.
ExStart State
On point-to-point networks, the two routers decide which router will initiate the DBD packet exchange and decide upon the initial DBD packet sequence number.
Exchange State
Routers exchange DBD packets. If additional router information is required then transition to Loading; otherwise, transition to the Full state.
Loading State
LSRs and LSUs are used to gain additional route information. Routes are processed using the SPF algorithm. Transition to the Full state.
Down State
No Hello packets received = Down. Router sends Hello packets. Transition to Init state.
