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Chapter5MACAddressT ableConguration
DynamicMACaddressesintheMACaddresstablearelearned
bytheswitch.TheprocedureofswitchlearningMACaddress
isasfollows:
SwitchanalyzesthesourceMACaddressandVLANID(forex-
ample,MAC1+VID1)onceitreceivesadataframeonaport.
IfjudgingtheMACaddresstobevalidandlearnable,theswitch
checksMAC1+VID1initsMACaddresstable.Iftheentryisnot
found,theaddressisaddedtotheMACaddresstable,other-
wisetheentryisupdated.
Note:
i.MACaddresslearningistolearnthesourceMACaddress
ofreceiveddataframes,notthedestinationMACaddress.
ii.MACaddresslearningappliestounicastaddressesonly,not
tobroadcastormulticastaddresses.
2.MACAddressAging
ThesizeoftheMACaddresstableislimited,soaMACaddress
agingmechanismisprovidedforeffectiveresourceutilityof
theMACaddresstable.
Aswitchconsidersadevicethathasgotofineorisnotin
communicationwhenitfailstoreceiveanydataframefrom
thatdeviceforacertaintimeperiod(setagingtime),thatis,it
doesnotreceiveanydataframefromitssourceMACaddress
asthatofdevice’sMACaddress.
ThentheswitchdeletesthatMACaddressofthedevicefrom
itsMACaddresstableandupdatestheMACaddresstable.
MACaddressagingappliestodynamicMACaddressesonly.
3.ManualAdditionandDeletion
AnentrycanbeaddedtotheMACaddresstableofaswitchwith
acongurationcommandwhenthenetworkisrelativelystable
anddeviceisconnectedtoaxedswitchport.Conguration
cantakeplacefordynamic,staticorpermanentMACaddress.
ConguringstaticorpermanentMACaddressescanprevent
MACspoongattacks.
MACaddresscanbedeletedwiththeMACaddressdeletion
command.DeletingcommandofZXR105900/5200can
forciblydeleteadynamicallylearnedMACaddress.
ConfiguringMACAddress
Table
MACaddresstableofswitchcanrunnormallywiththedefaultcon-
guration.ButsomeappropriatecongurationonMACaddress
tablecanimprovethenetworkstability.
CondentialandProprietaryInformationofZTECORPORATION33