LLDP (Link Layer Discovery Protocol) is a vendor-neutral Layer 2 protocol defined by the IEEE 802.1AB standard. It allows network devices to advertise essential information about themselves to directly connected neighbors on the same local network segment, facilitating device discovery and network topology mapping.

Each LLDP-enabled device periodically transmits LLDP Data Units (LLDPDUs) that include details such as:

  • System name and description
  • Port name and description
  • VLAN ID
  • MAC address
  • Power over Ethernet (PoE) capabilities
  • Network policy information (e.g., for VoIP)

This information helps construct a detailed topology map of the local network and is widely utilized by switches, IP phones, wireless access points, and other networked devices to identify one another, thereby streamlining configuration and troubleshooting processes.

Unlike Cisco’s proprietary CDP (Cisco Discovery Protocol), which operates exclusively between Cisco devices, LLDP is a vendor-neutral protocol supported by equipment from most manufacturers. This broad compatibility makes LLDP ideal for multi-vendor network environments.

LLDP enables devices to seamlessly integrate into standardized network infrastructures, enhancing network visibility and simplifying diagnostics regardless of the switch or network vendor in use.

LLDP support on devices

LLDP settings are not accessible through Control Hub like other device settings. Instead, these settings can only be managed locally on the device via SSH or the web interface, ensuring precise and secure control over this critical network function.

Key LLDP-Related Configurations:

  1. LLDP Mode
    • xConfiguration NetworkServices LLDP Mode: <Off | On |
        Passive>
    • Description: Enable or disable the LLDP (Link Layer Discovery Protocol) daemon. Note: When both LLDP and NetworkServices CDP Mode are enabled, network settings received via CDP take precedence over those received via LLDP.
    • Default: Passive
    • Passive: The device listens for LLDP messages on the network but does not transmit any LLDP information. This mode allows the device to receive LLDP data and use it to populate certain status nodes (e.g., LLDP xStatus) for informational purposes, without influencing VLAN or other network settings.
    • On: The device actively participates in LLDP by both sending and receiving LLDP messages, enabling full LLDP functionality including VLAN control and network topology discovery.
    • Off: LLDP is completely disabled; the device neither sends nor receives LLDP messages.
  2. Discovery Protocol SystemName
    • xConfiguration
        NetworkServices DiscoveryProtocol SystemName: <Auto | FQDN |
    SEPMAC>

    • Description: Selects the source for the System Name TLV (Type Length Value) included in outgoing CDP (Cisco Discovery Protocol) and LLDP (Link Layer Discovery Protocol) packets. The system name is derived either from the device's MAC (Media Access Control) address (SEPMAC) or its Fully Qualified Domain Name (FQDN).

    • Default: Auto
    • Auto: The system name adapts dynamically based on the active discovery protocol.
    • FQDN: Use FQDN in outgoing System Name TLV for both CDP and LLDP.
    • SEPMAC: Use SEPMAC in outgoing System Name TLV for both CDP and LLDP.

Learn more about the LLDP related configurations here

CDP and LLDP can operate simultaneously, but this requires the connected switch to provide consistent and aligned network information across both protocols to ensure accurate device discovery and configuration.