8/14/2019 114602369-VLAN

1/6

CS 158B Project report

Name: Elaine Lim & Allison Nham

Due ate: !arch "5# "$$5

VIRTUAL LOCAL AREA NETWORKS

1. Overview:

%he irtual Local Area Net'or(s )LAN* is a s'itch net'or( technolo+, that ena-les

'or(stations or e.ices /rom i//erent LAN se+ments lo+icall, +roupe to+ether re+arless o/

their +eo+raphical location0 n this paper# 'e 'ill introuce some (e, aspects o/ LAN an

iscuss the -ene/its o/ LAN an 'h, it is 'orth'hile0

2. How VLAN works:

A .irtual LAN is no i//erent /rom a traitional LAN# -ecause it is consiere as a

-roacast omain0 %his means e.er, -roacast pac(et propa+ates throu+h the net'or( 'ill -e

seen -, e.er, host on the net'or(0 n the traitional net'or(# i/ user 'ants to sen a pac(et to

the net'or(# his -roacast pac(et 'ill ha.e to tra.el to all other users on the LAN0 2hile this

ma(es sense /or some users 'ithin a 'or(+roup to see each other3s messa+es# it is unli(el, that

all users in a compan, 'oul 'ant to recei.e other3s messa+es0 As a result# a LAN is esi+ne

to e/ine smaller -roacast omains 'ithin a s'itch0 %his means each LAN is assi+ne an

ienti/ier an an, pac(et can onl, tra.el /rom one -roacast omain to another i/ -oth omains

ha.e the same ienti/ier0

3. Requiree!"s "o se" u# VLAN:

n orer to implement LAN in a net'or( en.ironment# 'e nee LAN4a'are

s'itchin+ e.ices that must either compl, 'ith EEE 8$"01 stanars or must ha.e a .enor4

speci/ic implementation o/ LAN0 %hese e.ices can -e intelli+ent s'itches# 'hich operate at

Pa+e 1 o/ 6

8/14/2019 114602369-VLAN

2/6

the !AC la,er# or routers# 'hich operate at the net'or( la,er o/ the 7S re/erence moel0

Althou+h a s'itchin+ e.ice is reuire to hanle a LAN /ormation# in realit, it is the so/t'are

that pro.ies LAN capa-ilities0 2ith LAN mana+ement so/t'are# the net'or( mana+er 'ill

-e a-le to recon/i+ure LAN in/rastructure# re+arless o/ 'here the resources or users are

locate0

$. T%#es o& VLAN:

Depenin+ on the .enors# LAN +roupin+ metho can -e i.ie into three +eneral

cate+ories: port4-ase +roupin+# !AC aress4-ase +roupin+ an protocol4-ase +roupin+0

A. Port-based grouping:

Port4-ase +roupin+ is the most common techniue in e/inin+ LAN mem-ership0Asits name implies# a port4-ase LAN allo's us to ha.e separate LANs amon+ ports on the

same s'itch0 %his means the net'or( mana+er can e/ine a mappin+ o/ LANs to a -unch o/

interconnecte s'itch ports0 9or eample# in a s'itch 'ith /i.e ports# ports 1# ;# an < -elon+ to

LAN 1# ports " an 5 -elon+ to LAN "0 / the user mo.es# the net'or( mana+er simpl,

e/ines their ne' port as a mem-er o/ their eistin+ LANs0 %his metho is eas, /or settin+ up

an monitorin+ a LAN +roup -ecause it 'or(s 'ell in a net'or( 'here the mo.ement o/ users

is hi+h0 =o'e.er# one ra'-ac( o/ LAN mem-ership e/inin+ -, port is that the net'or(

mana+er nees to recon/i+ure the mem-ership as the user mi+rates /rom one port to another0

B. MAC address-based grouping:

n this case# the net'or( mana+er +roups all mem-ers in a LAN to+ether -, means o/

!AC aresses0 Each s'itch trac(s the !AC aresses 'hich -elon+ to each LAN0 %he (e,

a.anta+e o/ this metho is the net'or( mana+er oes not nee to recon/i+ure the s'itch 'hen

the user mo.es to a i//erent port0 =o'e.er# there are some limitations 'ith !AC aress4-ase

Pa+e " o/ 6

8/14/2019 114602369-VLAN

3/6

+roupin+0 9irst# all users must -e con/i+ure initiall, at least in one LAN an this clearl,

-ecomes a hu+e 'or(loa /or a lar+e net'or( 'ith thousans o/ users0 n a share meia

en.ironment# LAN mem-ership e/ine -, !AC aress encounters a serious per/ormance

issue ue to the coeistence o/ mem-ers o/ i//erent LANs in the same s'itch port0 %o the en#

/or those Note-oo( PC users# the, nee to constantl, upate their LAN mem-ership as the

users mo.e aroun0

C. Protocol-based grouping:

n a protocol4-ase +roupin+# the LAN /ormation is -ase on P aress pre/i#

meanin+ it must -e -ase on the source aress in the P heaer0 Each s'itch must etermine

that the pac(et -ase on the protocol t,pe pro.ie in the La,er4; P heaer0 7ne o/ the

a.anta+es o/ protocol4-ase +roupin+ is that it allo's partitionin+ per protocol t,pe0 t also

allo's the users to ph,sicall, mo.e 'ithout loosin+ their mem-ership0 =o'e.er# one o/ the

isa.anta+es is that it can a//ect the net'or( per/ormance ue to the nee /or inspectin+ the

Net'or( la,er aress in the pac(et0 9inall,# the other limitation o/ the protocol4-ase LAN

+roupin+ is that 'or(stations 'ill -e runnin+ non4routa-le protocols that the La,er4; LAN

cannot hanle# li(e NetB7S0

'. VLANS e(ers)i#s:

n orer to etermine the LAN mem-ership amon+ s'itches across a net'or(# three

methos ha.e -een implemente: ta-le maintenance o.er si+nalin+# /rame ta++in+ an time4

i.ision multiplein+ )%D!*0

n the ta-le maintenance o.er si+nalin+# 'hen a host -roacasts its /irst /rame# the s'itch

retains the 'or(station>s !AC aress to+ether 'ith its LAN mem-ership in a cache aress

ta-le0 %hen this in/ormation 'ill -e -roacast continuousl, to all other s'itches on the net'or(0

Pa+e ; o/ 6

8/14/2019 114602369-VLAN

4/6

=o'e.er# the net'or( mana+er still nees to upate the aress ta-le manuall, i/ there is a

chan+e in LAN mem-ership0 !oreo.er# the cache aress ta-le nees to -e upate 'hen the

net'or( epans or ne' s'itches are ae into the net'or(0

2hen a s'itch 'ants to tal( to another s'itch# a /rame ta++in+ metho is use so that the

s'itch can (no' 'hich LAN a pac(et is intene /or0 %he -roacast pac(et is transmitte li(e

an, other pac(et o.er the net'or(0 =o'e.er# 'hen the s'itch recei.es the pac(et# it 'ill etract

the ta+ to o-tain LAN in/ormation0

n a %D! metho# channels are reser.e /or each LAN to support multiple net'or(

en.ironments0 Althou+h it reuces some o/ the o.erhea cause -, the t'o methos a-o.e# it

'astes -an'ith since a eicate time slot o/ one LAN cannot -e use -, another 'hen the

channel is not -us,0

*. T%#e o& +i!ks i! VLANs:

Depens on 'hat (in o/ en.ironment# there are t'o t,pes o/ lin(s in a LAN0 A

s'itche port can run on either access lin( or trun( lin( moe0 2hen a nee o/ connectin+ users

'ithin a sin+le LAN +roup arises# the access lin( metho 'oul -e use0 %he access lin( is

normall, a s'itche port in access moe that is attache to a 'or(station0 %he -roacast /rame

transmitte on an access lin( is similar to an, other Ethernet /rame0

n a case 'here 'e ha.e multiple LANs on a s'itch# 'e cannot simpl, connect them

'ith one another .ia a s'itch0 %o +et /rom one LAN to the other# the net'or( mana+er nees

to esta-lish a trun( lin( to connect t'o s'itches to a router0 9or eample# i/ user A on LANs1

'ante to tal( to user B on LANs"# he must tra.el /rom the s'itch to the router an then return

to the s'itch0 Because s'itches an routers are lo+icall, constructe# users ma, thin( that the,

are tal(in+ in the same ph,sical LAN se+ment0

Pa+e < o/ 6

8/14/2019 114602369-VLAN

5/6

,. -e!e&i"s o& VLANs:

=a.in+ iscusse some o/ the -asic concepts -ehin LANs# 'e no' /ocus on some

promisin+ a.anta+es that this technolo+, has contri-ute in the net'or( en.ironment0

A. Increasing performance:

LAN helps to increase per/ormance -, partitionin+ the net'or( into smaller -roacast

omains0 B, +roupin+ the users into a lo+ical net'or(# it impro.es the per/ormance -, limitin+

the -roacast tra//ic to a speci/ic net'or(0 As a result# there 'ill -e less tra//ic /or the net'or(

as a 'hole0

B. Improving manageability:

LAN also reuces the cost o/ mo.in+ an chan+in+ 'or(stations0 Since LAN

mem-ership is not -oune to a particular location in the net'or(# it allo's users to (eep their

ori+inal P aresses e.en 'hen the, mo.e to a i//erent ph,sical location 'ithout the nee o/

recon/i+uration the P aress0 %his pro.ies the net'or( mana+er 'ith the a-ilit, to mana+e

toa,>s ,namic net'or(s0 An -, +roupin+ the ph,sicall, scattere 'or(stations into a lo+ical

'or(+roup# this 'oul lea to a more mana+ea-le net'or(0

C. More security:

LAN also pro.ies increase securit, option0 Since a s'itch onl, sens pac(ets to

esi+nate recipients in the same su-net# the aministrator can +roup these users 'ho reuire

access to sensiti.e in/ormation into one separate LAN to separate them /rom the +eneral users0

D. Fleibility and scalability:

B, allo'in+ the speci/ic resources to o-tain the mem-ership in more than one LAN#

users on particular LANs can share resources 'ith other users /rom i//erent lo+ical LANs

'ithout the nee o/ ain+ aitional s'itches or routers0

Pa+e 5 o/ 6

8/14/2019 114602369-VLAN

6/6

. Co!/+usio!:

2e ha.e iscusse the topic o/ LANs# a ne' technolo+, that ser.es as a net'or(e

'or( +roup o/ users sittin+ lo+icall, close to+ether# althou+h their 'or(stations ma, actuall, -e

locate in i//erent +eo+raphical areas0 n conclusion# LAN net'or( technolo+, has promise

a ne' (in o/ net'or( esi+n tool that assists net'or( mana+er in aaptin+ the net'or( to /it a

competiti.e chan+in+ 'orl0

Re&ere!/es

10 Lammle# %o an =ales# ?e.in# CCNP Switching Study Guide# S,-e# nc0# "$$10"0 =el# @i-ert# Virtual LANs# ohn 2ile, & Sons# nc0# 10

;0 araarajan# Su-a# Virtual Local Area Networks#

http:'''0cis0ohiostate0eujaincis884