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UGANDA CHRISTIAN UNIVERSITYUGANDA CHRISTIAN UNIVERSITY
FACULTY OF SCIENCE AND TECHNOLOGYFACULTY OF SCIENCE AND TECHNOLOGY
Department of Information Technology Department of Information Technology
Computer Networks
Program !SIT "
#a$uar% Semester & "'()
*+ LAN STANDARDS, -IRELESS LANs a$.VLANS
Le/turer Re0e//a As11mwe
P2o$e Num0er3"45 *("677*6 488 9'*'8 4"" ':(
Ema1; ras11mwe
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Introduction
Range of technologies - also calledLAN Standards
Ethernet
Fiber Channel
Token Ring
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Ethernet and its Evolution
Standard Ethernet- !"b#s
Fast Ethernet- !!"b#s
$igabit Ethernet-$b#s
Ten-$igabit Ethernet- !$b#s
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Ethernet The IEEE &!2'% co((ittee has been the
(ost active in definingalternative #h)sicalconfigurations' To distinguish the various
i(#le(entations
that are available* theco((ittee has develo#ed a concisenotation+
,.ata rate 1$ =0ps,s1g$a;1$gmet2o., ma>1mumsegme$t;e$gt2in hundreds of (eters
The defined alternatives are sho.n inthe table sho.n in the
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!"b#s S#ecifications 1Ethernet
3
EEE &!2'% !"b#s 4h)sical La)er "ediu(alternatives
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!"b#s S#ecifications 1Ethernet
IEEE :'"+) ('=0ps P2%s1/a; La%er =e.1uma;ter$at1?es+
The defined alternatives for 10-Mbps are:
10BASE5:Specifies the use of 50-ohm coaxial cable
and Manchester digital signaling. Themaximum length of a cable segment is set at
500 meters. Can extend using up to 4 repeaters.5
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10BASE2: lower-cost alternative to 10BASE5
using a thinner cable, with fewer taps over a
shorter distance than the 10BASE5 cable.
10BASE-T:Uses unshielded twisted pair in a
star-shaped topology, with length of a link is
limited to 100 meters. As an alternative, an
optical fiber link may be used out to 500 m.
10BASE-F:Contains three specifications using
optical fibre6
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In teleco((unications and signal#rocessing* 0ase0a$.is an ad7ectivethat describes signalsand s)ste(s .hose range of
fre8uencies is (easuredfro( 9ero to a(a/i(u( band.idth or highest signalfre8uenc)'
Trans(ission of signals .ithout(odulation' In a baseband localnet.ork* digital signals are inserteddirectl) onto the cable as
voltage #ulses' The entires#ectru( of the cable is
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!:ASE-T+ ;T< stands for t.isted #air
and !:ASE-F+ ;F< stands
for o#tical fiber'
!:ase3-Thick Ethernet
!:ase2-Thin Ethernet
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IEEE &!2'% !!"b#s S#ecifications1Fast Ethernet
Fast Ethernet refers to a set ofs#ecificationsdevelo#ed b) the EEE &!2'% co((itteeto #rovide lo. cost*Ethernet co(#atible LANs o#erating at(''=0ps'
The blanket designation for thesestandards is!!:ASE-T
!
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!!"b#s Fast Ethernet
1 0 0 B A S E - T X 1 0 0B A S E -F X 1 0 0 B A S E - T 4
Transmiss ion
m e d i u m
2 pair , ST P 2 pair , Catego ry
5 U T P
2 opt ical f ibers 4 pair , Catego ry
3 , 4 , o r 5 UT P
Signal ing
technique
M L T - 3 M L T - 3 4 B 5 B , N R Z I 8 B 6 T , N R Z I
Da ta rate 1 0 0 M b p s 1 0 0 M b p s 1 0 0 M b p s 1 0 0 M b p sM a x i m u m
segm ent l ength
1 0 0 m 1 0 0 m 1 0 0 m 1 0 0 m
N e t w o r k s p a n 2 0 0 m 2 0 0 m 4 0 0 m 2 0 0 m
EEE &!2'% !!:ASE-T 4h)sical La)er "ediu(alternatives
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!!:ASE->
?ses a unidirectional data rate !! "b#s
over single t.isted #air or o#ticalfiber link
t.o #h)sical (ediu( s#ecifications one fort.isted #air kno.n as !!:ASE T> andone for o#tical fiber kno.n as !!:ASE-F> !!:ASE-T>
uses t.o #airs of t.isted-#air cable for t/@ r/ 1trans(ission and receiving
ST4 and Categor) 3 ?T4 allo.ed "TL-% signaling sche(e is used
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(''!ASE6F@
uses t.o o#tical fiber cables fort/ 1trans(ission @ r/
1rece#tion
(''!ASE6T8
esigned to #roduce a !!-"b#s datarate over lo.er-8ualit) Cat %Bcategor) %?T4 thus takes advantage of large
installed base of cat % in office buildings
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Full u#le/ #eration
Traditional Ethernet is half du#le/+ a stationcan either trans(it or receive a fra(e but itcannot do both si(ultaneousl) Bat the sa(e ti(e
?sing full-du#le/* station can trans(it and
receive si(ultaneousl) A !!-"b#s Ethernet ran in full-du#le/ (ode*
gives a theoretical transfer rate of 2!! "b#s
Stations (ust have full-du#le/ ada#ter cards
and (ust use s.itching hub
each station constitutes se#arate collisiondo(ain
CS"ABC algorith( no longer needed
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"i/ed Configurations
Fast Ethernet su##orts (i/ture of e/isting!-"b#s LANs and ne.er !!-
"b#s LANs
su##orting older and ne.er technologies
e'g' !!-"b#s backbone LAN su##orts !-"b#s hubs stations attach to !-"b#s hubs using!:ASE-T
hubs connected to s.itching hubs using!!:ASE-T
high-ca#acit) .orkstations and servers attachdirectl) to !B!! s.itches
s.itches connected to !!-"b#s hubs use
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$igabit Ethernet Configuration
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Fast Ethernet - etails
Sa(e (essage for(at as ! "b#s Ethernet Fast Ethernet (a) run in full du#le/ (ode
So effective data rate beco(es 2!! "b#s
Full du#le/ (ode re8uires star to#olog) .ith
s.itches
In fact* shared (ediu( no longer e/ists .hens.itches are used
no collisions* thus CS"ABC algorith( no longerneeded
but stations still use CS"ABC and sa(e(essage for(at is used for
back.ard co(#atibilit) reasons
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$igabit Ethernet
Strateg) sa(e as Fast Ethernet Ne. (ediu( and trans(issions#ecification
Retains CS"ABC #rotocol and fra(efor(at
Co(#atible .ith ! and !! "b#sEthernet
Dh) gigabit Ethernet !B!! "b#s load fro( end userscreates increasedtraffic on backbones
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$igabit Ethernet 4h)sical
!!!:ase-S> Short .avelength* (ulti(ode fiber
!!!:ase-L>
Long .avelength* "ulti or single (ode fiber
!!!:ase-C> A s#ecial ST4 1,23(
one for each direction !!!:ase-T
0 #airs* cat3 ?T4 1bidirectional
!! (
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!$b#s Ethernet
Dh) sa(e reasons+ increase in traffic* (ulti(ediaco((unications' etc'
4ri(aril) for high-s#eed* local backbone
interconnection bet.een large-ca#acit) s.itches Allo.s construction of "ANs
Connect geogra#hicall) dis#ersed LANs
ariet) of standard o#tical interfaces
1.avelengths and link distances s#ecified for !$b Ethernet
%!! ( to 0! k(s
full du#le/
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E/a(#le ! $igabit EthernetConfiguration
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!-$b#s Ethernet ata Rate and istance#tions 1Log Scale
We also have copper alternatives. 10GBASE-T uses Cat 6 up
to 55 m; Cat 6a improve! Cat 6" up to 100 m.
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Fibre Channel Re8uire(ents
full du#le/ links .ith t.o fibers #er link
!! "b#s to &!! "b#s on single line
su##ort distances u# to ! k(
s(all connectors high-ca#acit) utili9ation* distance insensitivit)
greater connectivit) than e/isting (ultidro#channels
broad availabilit) Support for multiple cost/performance levels, from
small systems to supercomputers
carr) (ulti#le e/isting interface co((and sets
for e/isting channel and net.ork
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Fiber Channel Ele(ents
The ke) ele(ents of a fiber channelnet.ork are the end s)ste(s alsocalled nodes* and the net.ork itself.hich consists of one or
(ore s.itching ele(ents' The collectionof s.itching ele(ents isreferred to as fabric'
These ele(ents are interconnected b)#oint-to-#oint links bet.een #orts onthe individual nodes and s.itches'
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Co((unication consists of thetrans(ission of fra(es across the#oint-to-#oint bidirectionallinks'
An) node can co((unicate .ith an)other node connectedto the sa(e fabric using the
services of the fabric' Routing done b)fabric
Fra(es (a) be buffered .ithin fabric(aking it #ossible for different nodes to
connect to the fabric at different data
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Fabric can be i(#le(ented as a singlefabric ele(ent .ith attached nodes-asi(#le star arrange(ent or
as a (ore general net.ork of fabricele(ents as sho.n in the figure in slide2&
Fiber net.ork is like a s.itching
net.ork in contrast tothe LANs shared (ediu(* this fiberneeds not get concerned .ith (ediu(
access control issues25
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Fiber scales easil) in ter(s of #orts*data rate and distancecovered' This a##roach#rovides great fle/ibilit)'
Fiber channel can readil) acco((odate
ne. trans(ission (edia and data ratesb) adding ne. s.itches .ith a nu(berof #orts to an e/istingfabric'
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Fiber Channel Net.ork
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TGEN RIN$ 1IEEE &!2'3 TGEN RIN$Standard
A Ring consists of a nu(ber of re#eaters
each connected to t.o others b)unidirectionaltrans(ission links to for( a single closed#ath' ata are transferred se8uentiall)*bit b) bit fro( one re#eater to the ne/t'
Each re#eater regenerates andretrans(its each bit' Fora ring to o#erate as a
co((unication net.ork*three functions arere8uired+
ata insertion
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These functions are #rovided b) there#eaters
ata are trans(itted in #ackets each of
.hich contains a destination addressfield'
As a #acket circulates #ast a re#eater
the address field isco#ied' If the attached stationrecogni9es the address the rest of the#acket is co#ied' %!
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Re#eaters #erfor( the data insertion andrece#tion function in
a (anner not unlike that of ta#s .hichserve as device attach(ent #oints
on a bus or tree'
ata re(oval ho.ever is (ore difficult ona ring' For a bus or tree* signals inserted
onto the line #ro#agate to the end#ointsand are absorbed b)ter(inators' Hence shortl) aftertrans(ission ceases* the bus or tree isclean of data'
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Ho.ever* because the ring is a closedloo#* a #acket .ill circulateindefinitel) unless it isre(oved'
A #acket (a) be re(oved b) theaddressed re#eater*alternativel) each #acket could be
re(oved b) the trans(itting
re#eater after it has (adeone tri# around the loo#' This latter
a##roach is (ore desirable because
' It #er(its auto(atic ackno.ledge(ent
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A variet) of strategies can be used todeter(ine ho. and .hen #acketsare inserted into the ring'
These strategies are in effect (ediu(access control #rotocols'The (ethod used is token ring'
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"ediu( Access Control
The token ring techni8ue is based on theuse of a s(all fra(e called a token thatcirculates .hen all stations are idle'
A station .ishing to trans(it (ust .aituntil it detects a token#assing b)' It then sei9es the
token b) changing one bit in the token.hich transfor(s itfro( a token to a start of fra(e
se8uence for a data fra(e'%0
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Dhen a station sei9es a token and begins
to trans(it a fra(e* there isno token on the ring so other stations.ishing to trans(it (ust .ait' The fra(eon the ring .ill (ake a round tri# and be
absorbed b) the trans(ittingstation' In the defaulto#eration the trans(itting station .ill
insert a ne. token on the ring .henboth of the follo.ing conditions
have been (et'
'The station has co(#leted trans(ission ofits fra(e
2' The leading edge of the trans(itted
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nce the ne. token has been insertedon the ring* another station 1ne/tdo.n-strea( .ith data to send .ill beable to sei9e the token and trans(it'
Note that under lightl) loaded conditions*there is so(e inefficienc) .ith token
ring because a station (ust .ait for thetoken to co(e around beforetrans(itting' %5
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Ho.ever under heav) loads* .hich is.hen it (atters* the ring functions in around robin fashion .hich isboth efficient and fair'
The #rinci#al advantage of token ring isthe fle/ible control over access
that it #rovides
The #rinci#al disadvantage .ith it is there8uire(ent for
token (aintenance' Loss of
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=ore o$ -1re;ess Networks
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Wireless Comes of Age
Guglielmo Marconi invented the wireless telegraphin 1896 Communication b encoding alphanumeric characters in
analog signal
!ent telegraphic signals across the Atlantic "cean Communications satellites launched in 196#s
Advances in wireless technolog $adio% television% mobile telephone% communication
satellites More recentl
&roadband wireless networ'ing% cellular technolog%=
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&roadband Wireless (echnolog
)igher data rates obtainable with broadband wirelesstechnolog
Graphics% video% audio
!hares same advantages of all wireless services*
convenience and reduced cost
!ervice can be deploed faster than fi+ed service
,o cost of cable plant
!ervice is mobile% deploed almost anwhere
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-imitations and .ifficulties of Wireless
(echnologies
Wireless is convenient and less e+pensive
-imitations and political and technical difficulties
inhibit wireless technologies
-ac' of an industr/wide standard
.evice limitations
0g% small -C. on a mobile telephone can onl
displaing a few lines of te+t
0g% browsers of most mobile wireless devices usewireless mar'up language 2WM-3 instead of )(M-
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DEFINITION OF A -IRELESS NET-OR
A $rou# of interconnected nodes that e/changeinfor(ation and share
resources through a .irelesstrans(ission (ediu(
TYPES OF -IRELESS NET-ORS
Direless 4AN
Direless LAN
Direless :roadband Direless DAN 1satellite * "icro.ave *''etc
Cellular Net.orks02
Ch t i ti # Wi l
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Characteristics o# Wireless
WA$s
Covers large geographical areas
Circuits provided b a common carrier
Consists of interconnected switching nodes
(raditional WA,s provide modest capacit 64### bps common
&usiness subscribers using (/1 service 5 144 Mbps
common
)igher/speed -1re;essWA,suse sate;;1te* and 1#sof Mbps common
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Characteristics o# Wireless %A$s
?sed to be a net.ork .ith high #rices* lo.data rates* occu#ational safet)concerns* and licensing re8uire(ents
4roble(s have been addressed and#o#ularit) of .ireless LANs has gro.nra#idl)'
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&i## ' t Wi l %A$
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&i##erences 'et(een Wireless %A$s
an! WA$s
!cope of a -A, is smaller
-A, interconnects devices within a single building
or cluster of buildings
-A, usuall owned b organi;ation that owns theattached devices
:or WA,s% most of networ' assets are not owned b
same organi;ation
nternal data rate of -A, is much greater
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(he ,eed for DirelessMA,s
(raditional point/to/point and switched networ'techni
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Direless Standards
4AN * LAN and "AN standards .eredefined b) IEEE and Industrial foru(s
A LAN standard define (edia* coding
sche(e* fra(e for( at * "AC#rotocol and other data link la)er#rotocols
E/a(#les of standards + Direless 4AN+ :luetooth * IEEE &!2'3
Direless LAN + IEEE &!2' 1a *b * g
:roadband Direless Net.orks + IEEE &!%'5
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Single Cell Direless LANConfiguration
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"ulti-Cell Direless LANConfiguration
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Infrastructure Direless LAN
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Add Hoc LAN
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Factors To Consider+ ForDireless LAN
Sa(e as an) LAN High ca#acit)* short distances* fullconnectivit)* broadcast ca#abilit)
Through#ut+ efficient use .ireless(ediu( Nu(ber of nodes+Hundreds of nodesacross (ulti#le cells
Connection to backbone LAN+ ?secontrol (odules to connect toboth t)#es of LANs
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Factors To Consider+ For Direless
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Factors To Consider For Direless
LAN
Service area+ !! to %!! ( Lo. #o.er consu(#tion+Need longbatter) life on (obile stations"ustnt re8uire nodes to (onitor access#oints or fre8uenthandshakes
Trans(ission robustness and
securit)+Interference #rone andeasil) eavesdro##ed
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C i
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Factors To Consider+ ForDireless LAN
Collocated net.ork o#eration+T.o or(ore .ireless LANs in sa(earea
License-free o#eration
HandoffBroa(ing+ "ove fro( one cell toanother
)na(ic configuration+ Addition* deletion*
and relocation of end s)ste(s
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Direless LAN A##lications
LAN E/tension Cross-:uilding Interconnect
No(adic Access
Ad Hoc Net.orking
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A li ti LAN t i
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A##lications - LAN E/tension
Saves installation of LAN cabling
Eases relocation and other (odifications tonet.ork structure
Direless LAN to re#lace .ired LANs has notha##ened
In so(e environ(ents* role for the .irelessLAN :uildings .ith large o#en areas
"anufacturing #lants* stock e/change trading
floors* .arehouses Historical buildings S(all offices .here .ired LANs notecono(ical
"a) also have .ired LAN
3&
A##lications
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A##lications Cross-:uilding Interconnect
Connect LANs in nearb) buildings 4oint-to-#oint .ireless link
Connect bridges or routers
Not a LAN #er se ?sual to include this a##lication under
heading of .ireless LAN
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A##lications - No(adic Access
Link bet.een LAN hub and (obile datater(inal
La#to# or note#ad co(#uter
Enable e(#lo)ee returning fro( tri# totransfer data fro( #ortable co(#uter toserver
Also useful in e/tended environ(ent such as
ca(#us or cluster of buildings ?sers (ove around .ith #ortableco(#uters
"a) .ish access to servers on .ired
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A li ti Ad H N t ki
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A##lications Ad Hoc Net.orking
4eer-to-#eer net.ork Set u# te(#oraril) to (eet so(e
i((ediate need
E'g' grou# of e(#lo)ees* each .ithla#to# or #al(to#* in business orclassroo( (eeting
Net.ork for duration of (eeting
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VLANs
LANs 1irtual LANs .ere introduced tohel# divide our #h)sical andlogical net.orks* .ithout additional coststo hard.are* b) using the sa(e s.itch'
Not all s.itches su##ort LANs* so inorder to (ake use of the(* )our
s.itch (ust su##ort the(' Joucan then define .hich #orts on )ours.itch .ill belong to the different LANs)ou .ill create'
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VLANs
For e/a(#le* )ou can configure )ours.itch .ith #orts *2*% and 0 as #art ofLAN No'* .hile #orts 3*5*6and & belong to LAN No'2' Jou
then configure all (achines in eachLAN to be #art of one logical net.ork*isolating the( fro( the rest'
All broadcasts* (ulticasts and other data
are #ro#agated onl) to the#orts that belong to the sa(eLAN fro( .hich the data ca(e fro(' 5%
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T2e Ne>t a$. Last Top1/
-ANs
S.itching
Routing
I4
So(e (ore #rotocols
Read about these in advance 50
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