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Configuring ospf, Ospf overview, Autonomous system – Brocade Network OS Administrator’s Guide v4.1.1 User Manual

Page 583

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Configuring OSPF

OSPF overview............................................................................................................. 583

Configuring OSPF......................................................................................................... 591

OSPF overview

Open Shortest Path First (OSPF) is a link-state routing protocol that uses link-state advertisements
(LSAs) to update neighboring routers about a router’s interfaces. Each router maintains an identical
area-topology database to determine the shortest path to any neighboring router.

OSPF is built upon a hierarchy of network components and areas. The highest level of the hierarchy is
the Autonomous System (AS). An autonomous system is defined as a number of networks, all of which
share the same routing and administration characteristics. A backbone area forms the core of the
network, connecting all other areas. Details of these and other OSPF components are provided below.

Autonomous System

An AS can be divided into multiple areas as shown in the figure below. Each area represents a
collection of contiguous networks and hosts (refer to

OSPF areas

on page 586). Areas limit the

amount of advertisements sent (called flooding) within the network. An area is represented in OSPF by
either an IP address or a number.

Network OS Administrator’s Guide

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