Enterasys Networks D-Series Link Aggregation Control Protocol (LACP)

Link Aggregation Control Protocol (LACP)

6-36 Port Configuration

Link Aggregation Control Protocol (LACP)

Usingmultiplelinkssimultaneouslytoincreasebandwidthisadesirableswitchfeature,which

canbeaccomplishedifbothsidesagreeonasetofportsthatarebeingusedasaLinkAggregation

Group(LAG).OnceaLAGisformedfromselectedports,problemswithloopingcanbeavoided

sincetheSpanningTreecantreatthisLAGasasingleport.

Enabledbydefault,theLinkAggregationControlProtocol(LACP)logicallygroupsinterfaces

togethertocreateagreaterbandwidthuplink,orlinkaggregation,accordingtotheIEEE802.3ad

standard.ThisstandardallowstheswitchtodeterminewhichportsareinLAGsandconfigure

themdynamically.SincetheprotocolisbasedontheIEEE802.3adspecification,anyswitchfrom

anyvendorthatsupportsthisstandardcanaggregatelinksautomatically.

802.3adLACPaggregationscanalsoberuntoend‐users(thatis,aserver)ortoarouter.

Foreachaggregatableportinthedevice,LACP:

• Maintainsconfigurationinformation(reflectingtheinherentpropertiesoftheindividuallinks

aswellasthoseestablishedbymanagement)tocontrolaggregation.

•ExchangesconfigurationinformationwithotherdevicestoallocatethelinktoaLink

AggregationGroup(LAG).

• AttachestheporttotheaggregatorusedbytheLAG,anddetachestheportfromthe

aggregatorwhenitisnolongerusedbytheLAG.

•Usesinformationfromthepartnerdevice’slinkaggregationcontrolentitytodecidewhether

toaggregateports.

TheoperationofLACPinvolvesthefollowingactivities:

•Checkingthatcandidatelinkscanactuallybeaggregated.

• ControllingtheadditionofalinktoaLAG,andthecreationofthegroupifnecessary.

• Monitoringthestatusofaggregatedlinkstoensurethattheaggregationisstillvalid.

•RemovingalinkfromaLAGifitsmembershipisnolongervalid,andremovingthegroupifit

nolongerhasanymemberlinks.

InordertoallowLACPtodeterminewhetherasetoflinksconnecttothesamedevice,andto

determinewhetherthoselinksarecompatiblefromthepointofviewofaggregation,itis

necessarytobeabletoestablish

•Agloballyuniqueidentifierforeachdevicethatparticipatesinlinkaggregation.

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.