LLDP

The Link Layer Discovery Protocol (LLDP) is a vendor-neutral link layer protocol in the Internet Protocol Suite used by network devices for advertising their identity, capabilities, and neighbors on an IEEE 802 local area network, principally wired Ethernet.[1] The protocol is formally referred to by the IEEE as Station and Media Access Control Connectivity Discovery specified in IEEE 802.1AB and IEEE 802.3-2012 section 6 clause 79.

LLDP performs functions similar to several proprietary protocols, such as Cisco Discovery Protocol, Foundry Discovery Protocol, Nortel Discovery Protocol and Link Layer Topology Discovery.

Information gathered

Information gathered with LLDP is stored in the device as a management information database (MIB) and can be queried with the Simple Network Management Protocol (SNMP) as specified in RFC 2922. The topology of an LLDP-enabled network can be discovered by crawling the hosts and querying this database. Information that may be retrieved include:

  • System name and description
  • Port name and description
  • VLAN name
  • IP management address
  • System capabilities (switching, routing, etc.)
  • MAC/PHY information
  • MDI power
  • Link aggregation

Configuration

  • Enable service with:

    set service lldp

Options

  • Configure a Define management-address:

    set service lldp management-address <x.x.x.x>

  • Define listening interfaces

    set service lldp interface <all|interface name>

  • LLDPd also implements an SNMP subagent. To Enable SNMP queries of the LLDP database:

    set service lldp snmp enable

  • Enable optional/other protocols

    set service lldp legacy-protocols cdp

    Supported legacy protocols:

  • cdp - Listen for CDP for Cisco routers/switches
  • edp - Listen for EDP for Extreme routers/switches
  • fdp - Listen for FDP for Foundry routers/switches
  • sonmp - Listen for SONMP for Nortel routers/switches

Display neighbors

  • Display with:

show lldp neighbors

Exemple:

[email protected]:~# show lldp neighbors
Capability Codes: R - Router, B - Bridge, W - Wlan r - Repeater, S - Station
                 D - Docsis, T - Telephone, O - Other
Device ID                 Local  Proto  Cap   Platform             Port ID
---------                 -----  -----  ---   --------             -------
swA309                    eth0   LLDP   ?     Cisco IOS Software,  GigE0/33
  • Options:
  • detail - Show lldp neighbors detail
  • interface - Show LLDP for specified interface

Troubleshooting

Use operational command show log lldp to display logs.