Specifications

Link Aggregation Control Protocol (LACP)
SecureStack C3 Configuration Guide 4-39
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.
LACP Operation
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tha t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.
•Ameansofidentifyingthe setofcapabilitiesassociatedwitheachportandwitheach
aggregator,asunderstoodbyagivendevice.
•AmeansofidentifyingaLAGanditsassociatedaggregator.
LACP Terminology
Table 4‐5defineskeyterminologyusedinLACPconfiguration.
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.
Table 4-5 LACP Terms and Definitions
Term Definition
Aggregator Virtual port that controls link aggregation for underlying physical ports. Each
SecureStack C3 module provides 6 aggregator ports, which are designated in
the CLI as lag.0.1 through lag.0.6.