Contents
What are the pre requisite to be OSPF neighbors?
OSPF Neighborship Requirements
- The devices must be in the same area.
- The devices must have the same authentication configuration.
- The devices must be on the same subnet.
- The devices hello and dead intervals must match.
- The devices must have matching stub flags.
What is the neighbor state when an ospfv3 adjacency is established?
In an already established OSPF adjacency, an OSPF state will transition from a FULL or 2-Way State to the Down State when the router Dead Interval Timer expires (4 x Hello Interval timer), which means OSPF has lost communication with its neighbor and is now considered non-reachable or dead.
How are the neighborship States used in OSPF?
These states are used to establish a neighborship between routers. To understand all these states, we will use two different routers. Their IP address and Router-ID is configured as shown below: It is the first state of the OSPF membership process.
What happens when a neighbor sends a DBD packet?
Note: Receiving a Database Descriptor (DBD) packet from a neighbor in the init state will also a cause a transition to 2-way state. Once the DR and BDR are elected, the actual process of exchanging link state information can start between the routers and their DR and BDR.
When does the full adjacent neighbor state change?
During the fully adjacent neighbor state, if a router doesn’t receive hello packet from a neighbor within the RouterDeadInterval time (RouterDeadInterval = 4*HelloInterval by default) or if the manually configured neighbor is being removed from the configuration, then the neighbor state changes from Full to Down.
What happens when a router becomes adjacent to a neighbor?
At this state, a router decides whether to become adjacent with this neighbor. On broadcast media and non-broadcast multiaccess networks, a router becomes full only with the designated router (DR) and the backup designated router (BDR); it stays in the 2-way state with all other neighbors.