User manual

 16‐PortGigabitEthernetPoE+Web‐ManagedSwitchwith2SFPPorts
50

6.7 SPANNINGTREEPROTOCOL(STP)
TheSpanningTreeProtocolcanbeusedtodetectanddisablenetworkloopsandtoprovidebackuplinksbetween
switches,bridgesorrouters.Thisallowstheswitchtointeractwithotherbridgingdevicesinyournetworktoensurethat
onlyonerouteexistsbetweenanytwostationsonthenetwork.Italsoprovidesbackuplinks,whichautomaticallytake
overwhenaprimarylinkgoesdown.Thespanningtreealgorithmssupportedbythisswitchincludetheseversions: 
 STP–SpanningTreeProtocol(IEEE802.1D)
 RSTP–RapidSpanningTreeProtocol(IEEE802.1w)
 MSTP–MultipleSpanningTreeProtocol(IEEE802.1s)
TheIEEE802.1DSpanningTreeProtocolandIEEE802.1wRapidSpanningTreeProtocolallowfortheblockingoflinks
betweenswitchesthatformloopswithinthenetwork.Whenmultiplelinksbetweenswitchesaredetected,aprimary
linkisestablished.Duplicatedlinksareblockedfromuseandbecomestandbylinks.Theprotocolallowsfortheduplicate
linkstobeusedintheeventofafailureoftheprimarylink.OncetheSpanningTreeProtocolisconfiguredandenabled,
primarylinksareestablishedandduplicatedlinksareblockedautomatically.Thereactivationoftheblockedlinks(atthe
timeofaprimarylinkfailure)isalsoaccomplishedautomaticallywithoutoperatorintervention.Thisautomaticnetwork
reconfigurationprovidesmaximumuptimetonetworkusers.However,theconceptsoftheSpanningTreeAlgorithmand
protocolareacomplicatedandcomplexsubjectandmustbefullyresearchedandunderstood.Itispossibletocause
seriousdegradationtonetworkperformanceiftheSpanningTreeisincorrectlyconfigured.Pleasereadthefollowing
beforemakinganychangesfromthedefaultvalues. 
TheSwitchSTPperformsthefollowingfunctions:
 Createsasinglespanningtreefromanycombinationofswitchingorbridgingelements.
 Createsmultiplespanningtrees–fromanycombinationofportscontainedwithinasingleswitch,inuser
specifiedgroups.
 Automaticallyreconfiguresthespanningtreetocompensateforthefailure,additionorremovalofanyelement
inthetree.
 Reconfiguresthespanningtreewithoutoperatorintervention.

BridgeProtocolDataUnits
ForSTPtoarriveatastablenetworktopology,thefollowinginformationisused:
 Theuniqueswitchidentifier
 Thepathcosttotherootassociatedwitheachswitchport
 Theportidentifier

