Avaya P580 - Manual (Page 419)

Avaya P550R, P580, P880, and P882 Multiservice Switch User Guide, Version 5.3.1 11-1
11 Configuring the OSPF
Routing Protocol
Overview
The following information and procedures provided in this chapter
pertain to layer 3 module configuration only:
■
What is OSPF?
■
Monitoring Switch Performance Using OSPF Statistics
■
NBMA IP Interfaces
What is OSPF?
OSPF (Open Shortest Path First) is a link state networking protocol.
Each router broadcasts a packet that describes it own local links.
Routers collect information from these broadcast packets to build
their own network routing tables. These packets that describe the
local links are short and cause less traffic congestion than Routing
Information Protocol (RIP), which broadcasts large routing tables.
OSPF bases its routing decision on the least-cost path. The cost is
administered value, usually based on line speed. If there are
multiple areas in an OSPF domain, there must be a backbone area,
identified as area 0. When areas are configure in the OSPF domain,
there are four basic router classifications:
■
Internal Router — router with all directly connected
networks belonging to the same area. Routers with only
interfaces in the backbone area also belong to this category
and have a single link-state database.
■
Area Border Router (ABR) — router that has directly
connected networks belonging to multiple areas. ABRs have
multiple link-state databases, one for each area, including the
backbone. ABRs summarize the networks in their areas and
advertise them onto the backbone area. The backbone, in
turn, distributes the information to the other areas.