LLDP information is visible on ESXi host but not on physical TOR switch with Mellanox adapters

Products

• VMware vSphere ESXi

Issue/Introduction

• In the vSphere Client, Link Layer Discovery Protocol (LLDP) information is visible for the physical adapters under *Configure > Physical Adapters > vmnicN.
• The vSphere Distributed Switch (VDS) is correctly configured for LLDP in Both or Advertise mode.
• Despite being visible on the host, the physical Top-of-Rack (TOR) switch receives no LLDP information from the ESXi host.
• Packet captures on the ESXi host confirm that LLDP frames are being sent out from the ESXi level toward the physical wire:
  
  • Capture incoming packets:   pktcap-uw --uplink vmnicX --dir 0 --ethtype 0x88cc
  • Capture outgoing packets:  pktcap-uw --uplink vmnicX --dir 1 --ethtype 0x88cc

Environment

VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x

Cause

This issue occurs because the Mellanox Network Interface Card (NIC) has a built-in hardware LLDP engine/agent in its firmware. When this hardware agent is enabled, it may 'trap' or drop outgoing LLDP packets generated by the ESXi before they reach the physical network wire, even though packet captures show the ESXi successfully forwarding them to the driver layer.

Resolution

To resolve this issue, the hardware-level LLDP agent on the Mellanox NIC must be disabled to allow the ESXi to manage discovery protocol propagation.

1. Verify OS Egress: Confirm LLDP packets are leaving the host by running:
   

   • Receiving from switch:

     # pktcap-uw --uplink vmnic0 --dir 0 --ethtype 0x88cc -c 2 -o - | tcpdump-uw -ner -
<Timestamp> <Source Mac> > 01:80:c2:00:00:0e, ethertype LLDP (0x88cc), length 703: LLDP, length 689: <Physical Switch FQDN>

   • Sending to physical switch:

     # pktcap-uw --uplink vmnic0 --dir 1 --ethtype 0x88cc -c 2 -o - | tcpdump-uw -ner -
<Timestamp>  <Source Mac> > 01:80:c2:00:00:0e, ethertype LLDP (0x88cc), length 218: LLDP, length 204: <ESXi FQDN>

     Note: If packets are seen here but not on the switch, the hardware is dropping them.
2. Disable Hardware LLDP: Contact your hardware vendor to obtain the specific firmware commands or tools required to disable the LLDP agent.
3. Firmware Check: Ensure the NIC is running the latest supported firmware version from the hardware vendor, as some updates provide toggles for discovery protocol behavior.

Additional Information

Determining Network/Storage firmware and driver version in ESXi
Unable to see LLDP information on ESXi hosts using Intel X710 (or any Intel 700 series) adapters with the i40en device driver