OSPF neighbor relation ship

[ilnaiduccna]

Hello,

Can any body give brief answers for below questions it would be appreciate.

1. What is the difference between OSPF neighbor relationships and adjacencies?

2. What is OSPF reliable update mechanism?

3. What is the difference between broadcast and non-broadcast?

Regards,

Naidu

[husycisco]

Hello Naidu,

1) These terms are used differently in different documentations. Usually they refer to same thing. Some also use "neighbor adjacencies". The official terms that are actually different is "peering relationship" and adjacency. Peering relationship is the process that starts with 2-way connectivity and ends with synchronizing route databases. Peering relationship is the essential process for OSPF routers to become adjacent.

2) For a Link State Update packet sent, router receives an Acknowledgement packet. That makes the process reliable just like the TCP protocol.

3) In a broadcast segment (Ethernet for eaxample), OSPF PDUs that form, keep adjecencies and contain route updates are sent to well known multicast addresses 224.0.0.6 and 224.0.0.5 . But in a non-broadcast segment (Point to point for example), multicast does not exist. You use "unicast" between peers, using the neighbor command.

Regards