Chapter12
LLDP
TableofContents
LLDPOverview..................................................................99
ConguringLLDP.............................................................100
LLDPCongurationExample.............................................100
LLDPOverview
LLDPLinkLayerDiscoveryProtocolisanewprotocoldenedin
802.1ab.Itmakestheadjacentdevicessendinformationtoeach
othertoupdatephysicaltopologyinformationandestablishde-
vicemanagementinformationbase.TheworkowofLLDPisas
follows:
1.sendlocaldevicelinkandmanagementinformationtoadjacent
device;
2.Localdevicereceivesadjacentdevicenetworkmanagement
information;
3.Storeadjacentdevicenetworkmanagementinformationinlo-
caldeviceMIBdatabase.Networkmanagementsoftwarecan
querydevicelayer2connectionstatusinMIBdatabase.
LLDPisnotcongurationprotocolofremotesystemorsignalcon-
trolprotocolbetweenports.LLDPcandiscovertheadjacentde-
viceslayer2congurationisnotsame,butitdoesn'tprovide
mechanismtosolvetheproblem,itonlyreportsthisproblemto
upperlayermanagementdevice.
Inaword,LLDPisakindofneighborndingprotocol.Itdenesa
standardforthenetworkdevicesintheEthernetsuchasswitch,
routerandwirelesslanaccesspoint.Itcanannounceitsexistence
toothernodesinthenetworkandsavediscoveryinformationof
everyneighbordevice.Forexample,deviceconguration,device
IDandotherinformationcanbeannouncedbythisprotocol
LLDPdenesacommonannouncementinformationset,atrans-
missionannouncementprotocolandakindofwaytosavethe
receivingannouncementinformation.Thedevicethatneedtoan-
nounceitsinformationcanputmultiplepiecesofannouncement
informationintooneLLDPDULinkLayerDiscoveryProtocolData
Unittotransmit.ThisLLDPDUcontainsastingofvariablelength
shortmessageunits,whichiscalledT ypeLengthValue(TLV).The
descriptionisasfollows:
�Typemeanstheinformationtypethatneedtosend;
�Lengthmeansinformationbytenumber;
CondentialandProprietaryInformationofZTECORPORATION99