3com S7906E Manuel De Montage

 

1-3 

Source 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.  

Type 

The 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.  

 

LLDP uses LLDPDUs to exchange information. An LLDPDU comprises multiple type, length, and value 

(TLV) sequences, each carrying a type of device information, as shown in 

. 

Figure 1-3 An LLDPDU 

 

 

 

An LLDPDU can carry up to 28 types of TLVs, of which the chassis ID TLV, port ID TLV, TTL TLV, and 

end of LLDPDU TLV (end TLV in the figure) are mandatory TLVs that must be carried and other TLVs 

are optional.  

TLVs are type, length, and value sequences that carry information elements, where the type field 

identifies the type of information, the length field indicates the length of the information field in octets, 

and the value field contains the information itself.  

LLDPDU TLVs fall into these categories: basic management TLVs, organizationally (IEEE 802.1 and 

IEEE 802.3) specific TLVs, and 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 thus are 

optional to LLDPDUs.  

1)  Basic management TLVs 

 lists the basic management TLV types currently in use. Some of them are mandatory to 

LLDPDUs, that is, must be included in every LLDPDU.  

Table 1-3 Basic LLDP TLVs 

Chassis ID 

Bridge MAC address of the sending device. 

Port ID 

ID of the sending port.  

If MED TLVs are included in the LLDPDU, the port ID TLV 
carries the MAC address of the sending port or the bridge MAC 
in case the port does not have a MAC address. If no MED TLVs 
are included, the port ID TLV carries the port name.  

Time To Live 

Life of the transmitted information on the receiving device.  

End of LLDPDU 

Marks the end of the TLV sequence in the LLDPDU. 

Mandatory