Link Layer Discovery Protocol (Lldp) - ZyXEL Communications GS3700 Series User Manual

Link Layer Discovery Protocol (LLDP)

35.1 LLDP Overview
The LLDP ( Link Layer Discovery Prot ocol) is a layer 2 prot ocol. I t allows a net work device t o
advert ise it s ident it y and capabilit ies on t he local net work. I t also allows t he device t o m aint ain and
st ore inform at ion from adj acent devices which are direct ly connect ed t o t he net work device. This
helps an adm inist rat or discover net work changes and perform necessary net work reconfigurat ion
and m anagem ent . The device inform at ion is encapsulat ed in t he LLDPDUs ( LLDP dat a unit s) in t he
form of TLV ( Type, Lengt h, Value) . Device inform at ion carried in t he received LLDPDUs is st ored in
t he st andard MI B.
The Swit ch support s t hese basic m anagem ent TLVs.
• End of LLDPDU ( m andat ory)
• Chassis I D ( m andat ory)
• Port I D ( m andat ory)
• Tim e t o Live ( m andat ory)
• Port Descript ion ( opt ional)
• Syst em Nam e ( opt ional)
• Syst em Descript ion ( opt ional)
• Syst em Capabilit ies ( opt ional)
• Managem ent Address ( opt ional)
The Swit ch also support s t he I EEE 802.1 and I EEE 802.3 organizat ionally- specific TLVs.
I EEE 802.1 specific TLVs:
• Port VLAN I D TLV ( opt ional)
• Port and Prot ocol VLAN I D TLV ( opt ional)
I EEE 802.3 specific TLVs:
• MAC/ PHY Configurat ion/ St at us TLV ( opt ional)
• Power via MDI TLV ( opt ional, For PoE m odels only)
• Link Aggregat ion TLV ( opt ional)
• Maxim um Fram e Size TLV ( opt ional)
The opt ional TLVs are insert ed bet ween t he Tim e To Live TLV and t he End of LLDPDU TLV.
The next figure dem onst rat es t hat t he net work devices Swit ches and Rout ers ( S and R) t ransm it
and receive device inform at ion via LLDPDU and t he net work m anager can query t he inform at ion
using Sim ple Net work Managem ent Prot ocol ( SNMP) .
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