Specifications

How Do I Implement VLANs?
March 15, 2011 Page 3 of 20
How Do I Implement VLANs?
Bydefault,allEnterasysswitchesrunin802.1QVLANoperationalmode.Allportsonall
EnterasysswitchesareassignedtoadefaultVLAN(VLANID1),whichisenabledtooperateand
assignsallportsanegressstatusofuntagged.Thismeansthatallportswillbeallowedtotransmit
frames
fromtheswitchwithoutaVLANtagintheirheader.Also,therearenoforbiddenports
(preventedfromtransmittingframes)configured.
YoucanusetheCLIcommandsdescribedinthisdocumenttocreateadditionalVLANs,to
customizeVLANstosupportyourorganizationalrequirements,andtomonitorVLAN
configuration.
Preparing for VLAN Configuration
AlittleforethoughtandplanningisessentialtoasuccessfulVLANimplementation.Before
attemptingtoconfigureasingledeviceforVLANoperation,considerthefollowing:
•WhatisthepurposeofmyVLANdesign?(Forexample:securityortrafficbroadcast
containment).
•HowmanyVLANswillberequired?
•Whatstations(endusers,servers,etc.)
willbelongtothem?
•Whatportsontheswitchareconnectedtothosestations?
•WhatportswillbeconfiguredasGARPVLANRegistrationProtocol(GVRP)awareports?
Determininghowyouwantinformationtoflowandhow yournetworkresourcescanbebestused
toaccomplishthiswillhelpyoucustomizethetasks
describedinthisdocumenttosuityourneeds
andinfrastructure.
Onceyourplanningiscomplete,youwouldproceedthroughthestepsdescribedinConfiguring
VLANsonpage9.
Understanding How VLANs Operate
802.1QVLANoperationdiffersslightlyfromhowaswitchednetworkingsystemoperates. These
differencesareduetotheimportanceofkeepingtrack ofeachframeanditsVLANassociationas
itpassesfromswitchtoswitch,orfromporttoportwithinaswitch.
VLANenabledswitchesactonhowframes
areclassifiedintoaparticularVLAN.Sometimes,
VLANclassificationisbasedontagsintheheadersofdataframes.TheseVLANtagsareaddedto
dataframesbytheswitchastheframesaretransmittedoutcertainports,andarelaterusedto
makeforwardingdecisionsbytheswitchandother
VLANawareswitches.Intheabsenceofa
VLANtagheader,theclassificationofaframeintoaparticularVLANdependsuponthe
configurationoftheswitchportthatreceivedtheframe.
ThefollowingbasicconceptsofVLANoperationwillbediscussedinthissection:
LearningModesandFilteringDatabases(page
4)
VLANAssignmentandForwarding(page4)
ExampleofaVLANSwitchinOperation(page5)