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1-3
An LLDPDU can carry up 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.
of LLDPDU TLV (end TLV in the figure) are mandatory TLVs that must be carried and other TLVs are
optional.
TLVs
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
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
Type
Description
Remarks
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
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
Port Description
Port description of the sending port.
System Name
Assigned name of the sending device.
System Description
Description of the sending device.
System Capabilities
Identifies the primary functions of the sending
device and the primary functions that have been
enabled.
Management Address
Management address used to reach higher level
entities to assist discovery by network
management, and the interface number and OID
(object identifier) associated with the address.
Optional
2) IEEE 802.1 organizationally specific TLVs
Table 1-4
IEEE 802.1 organizationally specific TLVs
Type
Description
Port VLAN ID
PVID of the sending port
Port And Protocol VLAN ID
Port and protocol VLAN IDs