Basic Concepts - 3Com 4500G Family Configuration Manual

Basic Concepts

LLDP frames
LLDP sends device information in LLDP data units (LLDPDUs). LLDPDUs are encapsulated in Ethernet
II or SNAP frames.
1) Ethernet II-encapsulated LLDP frame format
Figure 1-1 Ethernet II-encapsulated LLDP frame format
The fields in the frame are described in
Table 1-1 Description of the fields in an Ethernet II-encapsulated LLDP frame
Field
Destination MAC address
Source MAC address
Type
Data
FCS
2) SNAP-encapsulated LLDP frame format
Figure 1-2 SNAP-encapsulated LLDP frame format
0
Table 1-1:
The MAC address to which the LLDPDU is advertised. It is fixed to
0x0180-C200-000E, a multicast MAC address.
The MAC address of the sending port. If the port does not have a MAC
address, the MAC address of the sending bridge is used.
The Ethernet type for the upper layer protocol. It is 0x88CC for LLDP.
LLDP data unit (LLDPDU).
Frame check sequence, a 32-bit CRC value used to determine the
validity of the received Ethernet frame.
15
Destination MAC address
Source MAC address
Type
Data = LLDPU
(n bytes)
FCS
1-2
Description
31