Specifications

Configuring STP and RSTP
March 14, 2011 Page 16 of 29
SpanningTreetopology.Byadjustingthisvalue,youcanconfiguresupportforamaximum
diameterfromtheSTProotofupto40bridges.Bydefault,Enterasysswitchingdevicesareset
withamaximumagetimeof20seconds,supportinga20‐bridgespanfromtherootbridge.
Usethiscommand
toadjustthemaximumagesetting:
set spantree maxage agingtime
Validagingtimevaluesare6–40(seconds).
Setting the Maximum Configurable STPs
Bydefault,MultipleSpanningTreemodeisgloballyenabledonEnterasysswitching devicesand 
oneSpanningTreeisconfiguredasSpanningTreeID(SID)0.Asdescribedin“MaximumSTP
Capacities”onpage4,devicessupportdifferentnumbersofSpanningTreeinstances(including
SID0),dependingontheirmodeltype
andmemoryinstalled.SIDvaluesarefrom1to4094.
N‐Series,S‐Series,andK‐Seriesdevicesallowyoutosetthemaximumnumberofuserconfigured
SpanningTreesallowedonthedevice:
set spantree maxconfigurablestps numstps
ValidnumstpsvaluesforN‐Series,S‐Series,andK‐Seriesdevicesare:
•1–8forDFE‐GoldSeriesdevices
•1–64forDFE‐Diamond,DFE‐Platinum,andS‐Seriesdevices
•1–32forK‐Seriesdevices
Enabling the Backup Root Function
DisabledbydefaultonN‐Series,S‐Series,stackable,andstandaloneswitchdevices,thebackup
rootfunctionworksonlywhenthebackuproot‐enabledbridgeisdirectlyconnectedtotheroot
bridge.ItthenpreventsstaleSpanningTreeinformationfromcirculatingthroughoutthenetwork
intheeventthatthelinkbetween
therootbridgeandthebackuproot‐enabledbridgeislost.Ifthis
happens,thebackuprootwilldynamicallyloweritsbridgepriorityrelativetotheexistingroot
bridgeʹspriority,causingittoimmediatelybeselectedasthenewrootbridge.
Usethiscommandtoenablethebackuprootfunction
onaSID:
set spantree backuproot sid enable
WhenSNMPtrapmessagingisconfiguredandthebackuprootfunctionisenabled,atrap
messagewillbegeneratedwhenthebackupbecomesthenewrootofthenetwork.
Adjusting RSTP Parameters
Sincerapidlinkreconfigurationcanhappenonlyonapoint‐to‐pointlinkoranedgeport(aport
thatisknowntobeontheedgeofabridgedLAN),insomecasesyoumaywanttodefinethem
administratively.However,sinceedgeportandpoint‐to‐pointlinksare
automaticallydetectedon
Enterasysswitchingdevices,inmostcasesyouwillnotneedtochangethesedefaultport
designations.
Note: Adjusting this setting applies only to N-Series and S-Series devices.