Transmitting LLDP Messages

You can configure each port to transmit LLDP messages, receive LLDP messages, or both.

When configured to transmit LLDP messages, the LLDP agent running on the switch passes serially through the list of ports that are enabled for LLDP. For each LLDP-enabled port, the switch periodically sends out an untagged LLDP packet that contains the mandatory LLDP TLVs as well as the optional TLVs that are configured for advertisement. These TLVs are advertised to all neighbors attached to the same network. LLDP agents cannot solicit information from other agents by way of this protocol.

Note

When both IEEE 802.1X and LLDP are enabled on the same port, LLDP packets are not sent until one or more clients authenticate a port.

Also, LLDP MED TLVs are advertised only after an LLDP MED TLV is received on a port that is configured for LLDP MED. (See LLDP MED Optional TLVs.)

The source information for TLVs is obtained from memory objects such as standard MIBs or from system management information. If the TLV source information changes at any time, the LLDP agent is notified. The agent then sends an update with the new values, which is referred to as a triggered update. If the information for multiple elements changes in a short period, the changes are bundled together and sent as a single update to reduce network load.