ZyXEL GS-4012F/4024 User Manual download pdf (Page 160)

GS-4012F/4024 User’s Guide

Chapter 25 OSPF 160

CHAPTER 25

OSPF

This chapter describes the OSPF (Open Shortest Path First) routing protocol and shows you

how to configure OSPF.

25.1 Overview

OSPF (Open Shortest Path First) is a link-state protocol designed to distribute routing

information within an autonomous system (AS). An autonomous system is a collection of

networks using a common routing protocol to exchange routing information.

OSPF offers some advantages over traditional vector-space routing protocols (such as RIP).

The following table summarizes some of the major differences between OSPF and RIP.

25.1.1 OSPF Autonomous Systems and Areas

An OSPF autonomous system can be divided into logical areas. Each area represents a group

of adjacent networks. All areas are connected to a backbone (also known as area 0). The

backbone is the transit area to route packets between two areas. A stub area, at the edge of an

AS, is not a transit area since there is only one connection to the stub area.

The following table describes the four classes of OSPF routers.

Table 53 OSPF vs. RIP

OSPF RIP

Network Size Large Small (with up to 15 routers)

Metrics Bandwidth, hop count, throughput, round

trip time and reliability.

Hop count

Convergence Fast Slow

Table 54 OSPF: Router Types

TYPE DESCRIPTION

Internal Router (IR) An Internal or intra-area router is a router in an area.

Area Border Router (ABR) An Area Border Router connects two or more areas.

Backbone Router (BR) A backbone router has an interface to the backbone.

AS Boundary Router An AS boundary router exchanges routing information with routers in other

ASes.

1 ... 159 160 161 ... 326

No comments

ZyXEL GS-4012F/4024 User Manual Page 160