D-Link DES-3326S - Switch - Stackable Uživatelská příručka stáhnout pdf (Strana 133)

DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

Switch Management and Operating Concepts 133

receive particular link-state updates are located. This helps

ensure that routing updates are not flooded throughout the

entire network and to reduce the amount of bandwidth

consumed by updating the various router’s routing tables.

Areas establish boundaries beyond which link-state updates do

not need to be flooded. So the exchange of link-state updates

and the calculation of the shortest path tree are limited to the

area that the router is connected to.

Routers that have connections to more than one area are called

Border Routers (BR). The Border Routers have the

responsibility of distributing necessary routing information and

changes between areas.

Areas are specific to the router interface. A router that has all

of its interfaces in the same area is called an Internal Router.

A router that has interfaces in multiple areas is called a Border

Router. Routers that act as gateways to other networks

(possibly using other routing protocols) are called Autonomous

System Border Routers (ASBRs).

Link-State Packets

There are different types of link-state packets, four are

illustrated below:

• Router Link-State Updates − these describe a

router’s links to destinations within an area.

• Summary Link-State Updates – issued by Border

Routers and describe links to networks outside

the area but within the Autonomous System (AS).

• Network Link-State Updates – issued by multi-

access areas that have more than one attached

router. One router is elected as the Designated

Router (DR) and this router issues the network

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D-Link DES-3326S - Switch - Stackable Uživatelská příručka Strana 133