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Lldpdus, Tlvs, Protocols and standards – H3C Technologies H3C S12500-X Series Switches User Manual

Page 165: Configuring basic vlan settings

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Table 12 Fields in a SNAP-encapsulated LLDPDU

Field Description

Destination MAC address

MAC address to which the LLDPDU is advertised. It is the same as that for
Ethernet II-encapsulated LLDPDUs.

Source MAC address

MAC address of the sending port.

Type

SNAP type for the upper layer protocol. It is 0xAAAA-0300-0000-88CC
for LLDP.

Data LLDPDU.

FCS

Frame check sequence, a 32-bit CRC value used to determine the validity
of the received Ethernet frame.

LLDPDUs

LLDP uses LLDPDUs to exchange information. An LLDPDU comprises multiple TLV sequences. Each TLV

carries a type of device information, as shown in

Figure 51

.

Figure 51 LLDPDU encapsulation format

An LLDPDU can carry up to 32 types of TLVs. Mandatory TLVs include Chassis ID TLV, Port ID TLV, Time

to Live TLV, and End of LLDPDU TLV. Other TLVs are optional.

TLVs

TLVs are type, length, and value sequences that carry information elements.
LLDPDU TLVs include the following categories:

Basic management TLVs

Organizationally (IEEE 802.1 and IEEE 802.3) specific TLVs

LLDP-MED (media endpoint discovery) TLVs

Basic management TLVs are essential to device management. Organizationally specific TLVs and

LLDP-MED TLVs are used for enhanced device management; they are defined by standardization or other

organizations and are optional to LLDPDUs.

1.

Basic management TLVs

Table 13

lists the basic management TLV types. Some of them are mandatory to LLDPDUs (they

must be included in every LLDPDU).

Table 13 Basic management TLVs

Type Description

Remarks

Chassis ID

Specifies the bridge MAC address of the sending device.

Mandatory.

Port ID

Specifies the ID of the sending port.
If the LLDPDU carries LLDP-MED TLVs, the port ID TLV carries

the MAC address of the sending port. Otherwise, the port ID
TLV carries the port name.

Time to Live

Specifies the life of the transmitted information on the
receiving device.

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