chapter 1-campus network design and vlan-update 1

8/18/2019 Chapter 1-Campus Network Design and VLAN-update 1

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Campus Network

Design Topology andVirtual LANs


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Introduction

•

What is campus network?• Is a building group o! buildings all connected into one ent

network that consists o! many local area network"

• A campus network should be designed using smallbandwidth and small broadcast domains !or a#ailabiper!ormance"

• In LAN$ all nodes belong to a single broadcast doma

• This means all nodes in the same LAN can recei#ed tbroadcast packet e#en the packet is not meant !or th

• We can use VLAN to obtained this ob%ecti#es"


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&'ample ( Campus network


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Campus network based onhierarchical network topology•

Campus access layer• Campus distribution layer

• Campus core layer


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)panning tree protocol *)T+,

•

The topology o! a campus network design is o!ten determined b• )T+ is a protocol and algorithm$ documented in I&&&-./"0D"

• )T+ is used by switches to pre#ent loops occurring on a network

• 1ow it work?• The algorithm will disable unwanted links and blocking ports that could

• The network designer physically connects switches in a meshed

redundant topology $ )T+ creates a logical tree with no redunda

2e!( http(www"orbit3computer3solutions"com)panning3Tree3+rotocol33)T+3"php


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What )T+ do?

•

It ensures that there is only one logical path betwdestination on the network by intentionally blockredundant paths that could cause a loop"

• When a switch port detects a loop in the networblocks one or more redundant paths to pre#ent

!orming"• )T+ will choose one switch to be 4 2oot 5ridge6"

• 7ther switches select one o! its ports as 42oot +othen a 9designated port6 is chosen on each segmall other ports are closed down"


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2oles o! the ports

+ort 2ole Description

2oot +ort 2oot port is the nearest port to the root switchIt is in !orwarding state"

Designated port It !orwards data !rom the network segmentwhich connects to the root switch and data!rom the switch to the network segment it

connects to"Alternate port :or backup purpose" It will not !orward any dat

to the network segment it connects to"


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)T+ ;e'ample"

• )T+ has 0 root bridgeswitch and sets o!ports on other bridgesswitches that!orward tra identi!y the root bridge and helpother bridges compute their lowest3costpath to the root"

• When bridge port change state bridgessend topology change noti@cation5+D>s"

• 5ridges send con@guration 5+D>s e#ery/ seconds to maintain the spanning tree"


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Campus network ;Virtual LAN

•

A campus network should be designed using small bandwsmall broadcast domains"

• A bandwidth domain *also known as Collison domain, is ade#ices that share bandwidth and compete !or access to bandwidth"

• &'ample ( a traditional bus topology is a single bandwidth

• A switch di#ides up bandwidth domains and is o!ten usedconnect each de#ice so that the network consist o! manybandwidth domains"

• Compared to hub$ using switch $ the bandwidth domain cthe switch port and the de#ice that connects it"


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Continue""

•

A broadcast domain is a set o! de#ices that can each other6s broadcast !rames"

• A broadcast !rame is a !rame that is sent to the address ::(::(::(::(::(::"

• 5y de!aults switches do not di#ide broadcast dom

• The campus access layer should use switches anpro#ide broadcast control hence we need to useto accomplished this"


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VLAN o#er#iew

• A VLAN is an emulation o! a standard LAN that allows data ttake place without the traditional physical restraints placed network"

• VLAN standard( I&&& -./"0B

• VLAN di#ides a physical LAN into multiple logical broadcast

• A VLAN is a set o! LAN de#ices that belong to an administra

group"• VLAN allow a large $ at $ switch3based network to be di#ide

separate broadcast domains"

• A VLAN enabled switch oods a broadcast out only the portspart o! the same VLAN as the sending station"


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VLAN ;continue

•

In VLAN$ communication is allowed within a VLAN• No communication is allowed between VLANs"

• 2outer need to use to allow communication betwee*inter3VLAN communication,

• A VLAN has become a method to subdi#ided physic

switch3based LANs into many logical LANs"• It allow a larger$ at$ switch3based network to be di#

into separate broadcast domains"

• VLAN3enabled switch oods a broadcast out only ththat are part o! the same VLAN as the sending statio


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:undamental VLAN Designs

• >nderstand LAN @rst"

• )witch A connectsstations in network A$switch 5 connectstations in network 5"

• When station A sends abroadcast $ station A/

station AE recei#e thebroadcastFnone !romstations in network 5recei#ed the broadcast"

• Why ????

Switch A

Station A1Station A2Station A3

Network A

Switch B

Station B1Station B2Station

Network B


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A )witch with VLANs

DG/.0E 0H

Station A1 Station A2 Station A3

VLAN A

Station B1 Station B2 Station B3

VLAN B

• Two VLANs implemented in a singleswitch instead o! two separate physicalLANs"

• Any tra


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VLAN with multiple switches

• 5oth switches contains stations that are member o! VLAN A an

• 1a#e problemF"!orwarding o! broadcast$ multicast or unknowdestination !rames !rom a member o! a VLAN on one switch tomembers o! the same VLAN on the other switch"

• In this diagram ; all !rames going !rom )witch A to switch 5 tasame interconnection path"

• Need to recogniJe the incoming !ane belong to A or 5?

• 1ow?• As the !rame lea#es )witch A$ a special header is added to the !rame

• The tag consist a VLAN identi@er *ID, that speci@es to which VLAN thbelong"


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VLANs )pan )witches

DG/.0E 0K

Switch A


Switch B


Station A1 Station A2 Station A3 Station A4 Station A5 Station A6

VLAN B

VLAN A

VLAN B

VLAN A


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Inter3VLAN communication

•

Communications between VLANs ha#e to be donlayer E i"e" using router"

• Draw diagram


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VLAN 2outing ( +hysical Connec

•

&ach VLAN reuires one uniue physical link conwith one inter!ace o! router"• Disad#antages( costly and inese T2>NMIN to impro#e

• ultiple physical inter!aces are grouped to share

physical link"• Less cabling$ cost eOecti#e and uses only one router

• Draw diagram


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VLAN3ad#antages

•

Impro#e network per!ormance• 2educes unnecessary broadcast tra


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Disad#antages

•

Isolates layer / broadcast tra


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2e!erences

•

1uawei Tech

• Top-Down Network Design (3r !ition"# $r&ppenhei'er# isco $ress $)*%isher# A)g)s

chapter 1-campus network design and vlan-update 1

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