LLDP on OpenWrt

Bruce Ediger

Install and configure LLDP on OpenWrt Linux

This is on my Linksys WHW03 V1 Velop hardware, currently running OpenWrt 24.10.0, r28427-6df0e3d02a

  1. opkg update
  2. opkg install lldpd
  3. Review text configuration file /etc/config/lldp
  4. /etc/init.d/lldpd enable
  5. /etc/init.d/lldpd start

My server routes all my subnets right now. From my server, a WHW03 Velop shows up like this:

$ sudo lldpcli show neighbors
-------------------------------------------------------------------------------
LLDP neighbors:
-------------------------------------------------------------------------------
Interface:    eno1, via: LLDP, RID: 5, Time: 0 day, 00:07:53
  Chassis:     
    ChassisID:    mac c4:41:1e:4e:38:3f
    SysName:      Velop0
    SysDescr:     OpenWrt 24.10.0 @ Velop0
    MgmtIP:       10.0.0.77
    MgmtIface:    5
    MgmtIP:       fe80::c641:1eff:fe4e:383f
    MgmtIface:    2
    Capability:   Bridge, on
    Capability:   Router, on
    Capability:   Wlan, off
    Capability:   Station, off
  Port:        
    PortID:       mac c4:41:1e:4e:38:3f
    PortDescr:    br-lan
    TTL:          120

Interface eno1 is the name of the ethernet hardware on my server, not on the WHW03.

From the WHW03 V1 (Velop) side, LLDP info looks like this:

LLDP neighbors:
-------------------------------------------------------------------------------
Interface:    br-lan, via: LLDP, RID: 1, Time: 0 day, 00:00:42
  Chassis:     
    ChassisID:    mac 44:a8:42:2d:c2:55
    SysName:      monarch.glump
    SysDescr:     Arch Linux Linux 6.13.11-hardened1-1-hardened #1 SMP PREEMPT_DYNAMIC Thu, 17 Apr 2025 22:27:54 +0000 x86_64
    MgmtIP:       10.0.0.1
    MgmtIface:    2
    MgmtIP:       fe80::46a8:42ff:fe2d:c255
    MgmtIface:    2
    Capability:   Bridge, off
    Capability:   Router, on
    Capability:   Wlan, off
    Capability:   Station, off
  Port:        
    PortID:       mac 44:a8:42:2d:c2:55
    PortDescr:    eno1
    TTL:          120

group_fwd_mask

Apparently, the OpenWrt br-lan device doesn’t ordinarily forward LLDP packets. LLDP packets aren’t TCP/IP packets at all. They’re ethernet protocol 0x88cc packets, where IP packets are ethernet protocol or ethertype 0x0800. LLDP packets get sent to a MAC address like 01:80:c2:00:00:0e. I found a blog post about how to enable forwarding LLDP packets. I did this logged in to my Velop:

$ cd /sys/class/net/br-lan/bridge
$ echo 16384 > group_fwd_mask

Once I did this, I could see my server’s LLDP info from the Velop.

tcpdump LLDP packets

Initially, lldpcli did not show me my server’s LLDP info. I installed tcpdump on a Velop with opkg install tcpdump.

On the Velop:

tcpdump -i br-lan ether proto 0x88cc

This showed me only LLDP packets from my server. On the server:

tcpdump -i ens4 ether proto 0x88cc

This showed me both server and Velop LLDP packets.