Specifications

Configuring and Managing VLANs
4-16 Configuring and Managing Ports and VLANs
Traffic Forwarding
ARoamAboutswitchestrafficatLayer2amongportsinthesameVLAN.Forexam ple,suppose
youconfigureports1and2tobelongtoVLAN2andports3and4tobelongtoVLAN3.Asa
result,trafficbetweenport1andport2isswitched,buttraffic
betweenport1andport3isnot
switchedandneedstoberoutedbyanexternalrouter.
802.1Q Tagging
ThetaggingcapabilitiesoftheRoamAboutSwitchareveryflexible.Youcan assign802.1Qtag
valuesonaper‐VLAN,per‐portbasis.ThesameVLANcanhavedifferenttagvaluesondifferent
ports.Inaddition,thesametagvaluecanbeusedbydifferentVLANsbutondifferentnetwork
ports.

Ifyouuseatagvalue,Enterasys NetworksrecommendsthatyouusethesamevalueastheVLAN
number.MSSdoesnotrequiretheVLANnumberandtagvaluetobethesame,butsomeother
vendors’devicesdo.
MSSautomaticallyassignstagvaluestoAPs.Eachofthesetagvaluesrepresents
aunique
combinationof radio,encryptiontype,andVLAN.Thesetagvaluesdonotnecessarilycorrespond
totagvaluesyouconfigureontheVLANportsthroughwhichtheAPisconnectedtothe
RoamAboutSwitch.
Tunnel Affinity
RoamAboutswitchesconfiguredasaMobilityDomainallowuserstoroamseamlesslyacross
DAPsandevenacrossRoamAboutswitches.Althoughaswitchthatisnotamemberofauser’s
VLANcannotdirectlyforwardtrafficfortheuser,theswitchcan tunnelthetraffictoanother
RoamAboutSwitchthatisa
memberoftheuser’sVLAN.
IftheRoamAboutSwitchthatisnotintheuser’sVLANhasachoiceofmorethanoneother
RoamAboutSwitchthroughwhichtotunneltheuser’straffic,theswitchselectstheotherswitch
basedonan affinityvalue.Thisisanumericvaluethateach
RoamAboutSwitchwithinaMobility
Domainadvertises,foreachofitsVLANs,toallotherswitchesintheMobilityDomain.Aswitch
outsidetheuser’sVLANselectstheotheroperationalswitchthathasthehighestaffinityvaluefor
theuser’sVLANtoforwardtrafficfortheuser.
Ifmorethan
oneRoamAboutSwitchhasthehighestaffinityvalue,MSSrandomlyselectsoneof
theswitchesforthetunnel.
Configuring a VLAN
YoucanconfigurethefollowingVLANparameters:
•VLANnumber
•VLANname
•Portlist(theportsintheVLAN)
•Per‐porttagvalue(an802.1QvaluerepresentingavirtualportintheVLAN)
•Tunnelaffinity(avaluethatinfluencestunnelingconnectionsforroaming)
Note: Do not assign the same VLAN multiple times using different tag values to the same network
port. Although MSS does not prohibit you from doing so, the configuration is not supported.