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14 LLDP
LLDP is a neighbor discovery protocol that is used for network devices to advertise information about
themselves to other devices on the network. This protocol runs over the data-link layer, which allows two
systems running different network layer protocols to learn about each other.
Devices in a LAN maintain operations-related configuration information in management information bases
(MIBs). LLDP helps avoid misconfiguration problems in LANs by enabling LAN devices to be aware of other
devices' configuration information.
LLDP supports a set of attributes that it uses to discover neighbor devices. These attributes contain type,
length, and value descriptions and are referred to as TLVs. LLDP supported devices can use TLVs to receive
and send information to their neighbors. Details such as configuration information, device capabilities, and
device identity can be advertised using LLDP.
Supermicroswitches provides the following LLDP features:
• Support all mandatory TLVs (chassis identifier, port identifier and time-to-live).
• Support optional TLVs - port description, system name, system description, system capabilities and
management address.
• Support organizationally specific optional TLVs - port VLAN identifier, port and protocol VLAN
identifier, VLAN name, MAC or PHY configuration or status, link aggregation and maximum frame
size.
• Provide support for notifications through traps.
An LLDP agent operates in any one of the following three modes:
1. Transmit-only mode: The agent can only transmit the information about the capabilities and the
status of the local system.
2. Receive-only mode: The agent can only receive information about the capabilities and the status of
the remote systems.
3. Transmit and receive mode: The agent can transmit the local system capabilities and status
information and receive the capabilities and status informationof remote systems.
The LLDP transmit only modesends the local device's information at regular intervals in LLDP TLV’s.
Whenever the transmit mode is disabled, the device transmits an LLDP PDU with a time-to-live (TTL) TLV
containing "0" in the information field. Upon reception of a PDU with TLV 0, remote devices are then
enabled to remove the information associated with this local device fromtheir databases.
The LLDP receive only mode receivesaremote device's information and updates the remote system's LLDP
MIB database. When new or updated information is received, the receive module initiates a timer for
avalid duration indicated by the TTL TLV in the received LLDP PDU. The remote system's information is
removed from the database when an LLDP PDU is received with TTL TLV containing "0" in its information
field.
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