User`s guide

Configuring STP and RSTP
5-12 Configuring Spanning Trees
Defining the Maximum Age
IfabridgedoesnothearBPDUsfromtherootbridgewithinaspecifiedinterval,itassumesthat
thenetworkhaschangedandrecomputesthespanningtreetopology.
Toadjustthemaximum agesetting:
set spantree maxage agingtime
Validagingtimevaluesare6‐40.
Setting the Maximum Configurable STPs
Bydefault,thedeviceisrunninginMSTPmodeand,dependingonthemodeltypeandmemory
installed,willallowyoutoconfigureupto33spanningtreeinstances.
Toadjustthemaximum configurablenumberofspanningtreesallowedonthedevice:
set spantree maxconfigurablestps numstps
Validnumstpsvaluesare:
•1‐9forMatrixDFE‐GoldSeriesmodules,
•1‐33forMatrixDFE‐PlatinumSeriesorN‐SAdeviceswith128MBofmemoryinstalled
(devicedefault),or
•1‐64forMatrixDFE‐PlatinumSeriesorN‐SAdeviceswithandadditional128MB
memoryupgradeinstalled.
Enabling the Backup Root Function
Disabledbydefault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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.
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SIDbecomesthenewrootofthenetwork.
Adjusting RSTP Parameters
Sincerapid(one‐second)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MatrixDFESeriesandN‐SAdevices,inmostcasesyouwillnotneedtochangethese
defaultportdesignations.