The transmission and reception of LLDPDUs are enabled when LLDP is enabled on a port. The LLDP agent operates in any of the following modes:

  • Transmit-only mode

  • Receive-only mode

  • Transmit-and-receive mode

    When LLDP transmission is enabled, the LLDP agent advertises information to neighbors at regular, user-configured intervals. When LLDP reception is enabled on a port, the LLDP agent receives advertised information from remote neighboring devices and stores this data in the remote systems’ MIB.


    On Cisco devices, if both LLDP and Cisco Discovery Protocol (CDP) are enabled, LLDP will be given priority and connections will be created using LLDP. If LLDP is enabled on a device, and CDP is enabled on a different device, connection is created only as a bridge.

    It is important for both endpoints to support LLDP (meaning LLDP enabled) but at least one endpoint should have LLDP MIB support. The other endpoint should have basic MIB support to figure out the port and interface.