D-Link DES-3326S manual Link-State Packets, 133

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

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

Switch Management and Operating Concepts 133