Connecting LANs, Backbone Networks, and

Virtual LANs

01204325: Data Communication and Computer Networks

Asst. Prof. Chaiporn Jaikaeo, Ph.D.chaiporn.j@ku.ac.th

http://www.cpe.ku.ac.th/~cpjComputer Engineering Department

Kasetsart University, Bangkok, ThailandAdapted from lecture slides by Behrouz A. Forouzan© The McGraw-Hill Companies, Inc. All rights reserved

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Outline Network connecting devices Backbone networks Virtual LANs

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Network Connecting Devices

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Layer-1 Connecting Devices

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Repeaters Connected segments become single

collision domain

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Repeater Function

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Hubs Similar to multiport repeaters All segments belong to the same

collision domain

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Layer-2 Connecting Devices

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Bridges Bridges process information up to the

frame-level (layer 2)

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Bridges Connecting LANs while separating collision

domains MAC addresses are used for filtering Connected segments form a single network

(same broadcast domain)

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Learning Bridges

A D

E A

B C

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Loop Problem

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Graph Representation

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Creating Spanning Tree

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Blocking Ports

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Switches Similar to multiport bridges Also run Spanning-Tree Protocol

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Layer-3 Connecting Devices

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Routers Capable of connecting networks of

different types Routers separate networks into

different broadcast domains

Backbone Networks

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Bus Backbone

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Star Backbone

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Connecting Remote LANs

Virtual LANs

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Regular Switch Three LANs are connected by a regular

switch, forming one LAN (one broadcast domain)

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Switch with VLAN Feature Different VLANs belong to different broadcast

domains They are considered isolated networks

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Multiple VLAN Switches

Trunk Trunk

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Routing Across VLANs Router is required to connect

different VLANs

Trunk Trunk

Trunk