See also: lldpd upstream documentation

The goal of LLDP is to provide an inter-vendor compatible mechanism to deliver Link-Layer notifications to adjacent network devices.

An implementation of IEEE 802.1ab

lldpd (Link Layer Discovery Protocol daemon) daemon providing an industry standard protocol designed to supplant proprietary Link-Layer protocols such as Extreme's EDP (Extreme Discovery Protocol) and CDP (Cisco Discovery Protocol).

OpenWRT uses the standard, lightweight lldpd package. Drop into your ER-X via SSH:

opkg update
opkg install lldpd

Alternatively/additionally install luci-app-lldpd package to add Luci Web interface for LLPD - discovered information are neatly presented in GUI.

LLDP frames are link-local frames, do not use any network interfaces other than the ones that achieve a link with its link partner, and the link partner being another networking device. Do not use bridge,VLAN, or DSA conduit interfaces.

Example /etc/config/lldpd, start lldpd on all interfaces:

config lldpd config
       # lldp defaults to listening on all interfaces
       # Set class of device
       option lldp_class 4
       # if empty, the distribution description is sent
       option lldp_description "OpenWrt System"

daemon must be running for lldpcli to work

View neighbors across each enabled interface.

lldpcli show neighbors

Get statistics about which interfaces are sending/receiving LLDP frames:

lldpcli show statistics

- lldpd unable to receive frames on mediatek due to bug: https://github.com/openwrt/openwrt/issues/13788

It has been confirmed that on MediaTek (i.e. on ER-X, 25.12.4), the following configuration file works well:

config lldpd config
        option enable_cdp 1
        option enable_fdp 1
        option enable_sonmp 1
        option enable_edp 1

        option lldp_class 4
        option lldp_location "address country EU"

        # interfaces to listen on
        list interface "loopback"
        list interface "eth1"
        list interface "eth2"
        list interface "eth3"
        list interface "eth4"