Link Aggregation Control Protocol (LACP)
5-34 Port Configuration
Example
ThefollowingexampleclearsVLAN2frombeingusedforremoteportmirroring.
B3(su)->clear mirror vlan 2
Link Aggregation Control Protocol (LACP)
Usingmultiplelinkssimultaneouslytoincreasebandwidth isadesirableswitchfeature,which
canbeaccomplishedifbothsidesagreeonasetofportsthatarebeingusedasaLinkAggregation
Group(LAG).OnceaLAGisformedfromselectedports,problemswithloopingcanbeavoided
sincethe
SpanningTreecantreatthisLAGasasingleport.
Enabledbydefault,theLinkAggregationControlProtocol(LACP)logicallygroupsinterfaces
togethertocreateagreaterbandwidthuplink,orlinkaggregation,accordingtotheIEEE802.3ad
standard.ThisstandardallowstheswitchtodeterminewhichportsareinLAGsand
configure
themdynamically.SincetheprotocolisbasedontheIEEE802.3adspecification,anyswitchfrom
anyvendorthatsupportsthisstandardcanaggregatelinksautomatically.
802.3adLACPaggregationscanalsoberuntoend‐users(thatis,aserver)ortoarouter.
LACP Operation
Foreachaggregatableportinthedevice,LACP:
• Maintainsconfigurationinformation(reflectingtheinherentpropertiesoftheindividuallinks
aswellasthoseestablishedbymanagement)tocontrolaggregation.
•Exchangesconfigurationinformationwithotherdevicestoallocate thelinktoaLink
AggregationGroup(LAG).
• Attachestheporttotheaggregatorused
bytheLAG,anddetachestheportfromthe
aggregatorwhenitisnolongerusedbytheLAG.
•Usesinformationfromthepartnerdevice’slinkaggregationcontrolentitytodecidewhether
toaggregateports.
TheoperationofLACPinvolvesthefollowingactivit ies:
•Checkingtha tcandidatelinkscanactuallybeaggregated.
• Controllingthe
additionofalinktoaLAG,andthecreationofthegroupifnecessary.
• Monitoringthestatusofaggregatedlinkstoensurethattheaggregationisstillvalid.
•RemovingalinkfromaLAGifitsmembershipisnolongervalid,andremovingthegroupifit
nolongerhas
anymemberlinks.
Caution: Link aggregation configuration should only be performed by personnel who are
knowledgeable about Spanning Tree and Link Aggregation, and fully understand the ramifications
of modifications beyond device defaults. Otherwise, the proper operation of the network could be
at risk.
Note: Earlier (proprietary) implementations of port aggregation referred to groups of aggregated
ports as “trunks”.
Note: A given link is allocated to, at most, one Link Aggregation Group (LAG) at a time. The
allocation mechanism attempts to maximize aggregation, subject to management controls.