Neighbor and Adjacency Initialization

Neighbor and Adjacency Initialization
Neighbor/adjacency formation is a very big part of OSPF operation. These relationships are often
easily formed over point-to-point connections, but much more complex procedures are required
when multiple OSPF routers are connected via a broadcast multi-access medium.
The Hello protocol is used to discover neighbors and establish adjacencies. Hello packets
contain a great deal of information regarding the originating router. Hello packets are multicast
or unicast out every interface on a 10-second interval for point-to-point and broadcast multiaccess
interfaces and on a 30-second interval for NBMA interfaces, by default. The data contained
in the Hello packet can be seen in Table 5.1. It is important to remember that the router
ID, area ID, and authentication information are carried in the common OSPF header. The Hello
packet uses the common OSPF header.