To troubleshoot OSPF, it is important to understand how OSPF routers traverse different OSPF states when adjacencies are being established.
The figure lists the OSPF states and provides a summary of functions of each state.
When troubleshooting OSPF neighbors, be aware that the FULL or 2WAY states are normal. All other states are transitory; that is, the router should not remain in those states for extended periods of time.