3Com CoreBuilder 3500, Implementation Manual

Page: 395 / 592

Neighbors 395
Static Neighbors On broadcast networks such as Ethernet, the OSPF Hello protocol uses
the broadcast capability to dynamically discover neighbors. On
nonbroadcast networks, such as X.25 Public Data Network, however, you
may need to assist in neighbor discovery by statically defining neighbors
on each interface. OSPF then uses the Hello protocol to maintain the
neighbors that you statically define.
When you statically define a neighbor on the system, you specify both
the router interface to which you want to add the neighbor and the IP
address of the neighboring router that you want to associate with the
specified interface. The Hello protocol then dynamically retrieves the
additional neighbor information, as described in “Neighbor Information”
in the previous section.
Important
Considerations
Consider the following guidelines when you configure neighbors:
■
Routers use OSPF hello packets to learn neighbor addresses
dynamically on broadcast networks.
■
Define static neighbors only on nonbroadcast interfaces, because
neighbors are not learned dynamically on nonbroadcast networks.
■
Hello packets are the only OSPF packet type that is processed by all
routers within an area. All other packet types are sent and received
only on adjacencies.
■
Neighbor adjacencies cannot be formed if two routers have different
Hello intervals, Dead intervals, or passwords.