OSPF neighbors

In OSPF, routers have to become neighbors first before exchanging link- state advertisements (LSA).After configuring OSPF on routers it will start sending hello packets to each other.The Hello packets also serve as keepalives to allow routers to quickly discover if a neighbor is down. Hello packets also contain a neighbor field that lists the Router IDs of all neighbors the router is connected to.

OSPF routers will only become neighbors if the following parameters within a Hello packet are identical on each router: 

  • Area ID 
  • Subnet Mask 
  • Hello Interval 
  • Dead Interval 
  • Authentication 
Enhanced by Zemanta


  1. STUB flag should match for OSPF routers to become neighbors.

  2. Subnet mask? Can you elaborate this part please?

    1. Both interfaces should have same subnet mask