CDP information unavailable on ESXi physical network adapters

Products

• VMware vSphere ESXi

Issue/Introduction

• On an ESXi host, the following error message appears when attempting to view Cisco Discovery Protocol (CDP) details for a physical network adapter

Cisco Discovery protocol is not available on this physical network adapter

Environment

VMware vSphere ESXi 8.x

Cause

To view CDP information on ESXi network adapters, the following requirements must be met:

• The ESXi host must be configured to listen for CDP information.
• The upstream physical switch must be advertising CDP information.
• CDP must be enabled on both the ESXi virtual switch (Standard or Distributed) and the physical switch ports

This issue can occur if Cisco Discovery protocol(CDP) is not enabled on ESXi host or upstream physical switch

Resolution

• Ensure CDP is enabled on both the ESXi host and the physical switch.

Enable Cisco Discovery Protocol on a vSphere Standard Switch

Standard switches require the use of the ESXi command line for CDP configuration:

• Log in to the ESXi host via SSH as root.
• Check the current CDP status (e.g., for vSwitch0): esxcfg-vswitch -b vSwitch0
• Is the CDP status is down, set the CDP status to listen: esxcfg-vswitch -B listen vSwitch0
• Verify the change: esxcfg-vswitch -b vSwitch0

Enable Cisco Discovery Protocol on a vSphere Distributed Switch

For Distributed Switches (vDS), manage settings via vCenter Server:

• Navigate to the vDS in the vSphere Client.
• Edit the vDS settings and set the discovery protocol to Cisco Discovery Protocol.
• Select the operation mode to Listen

Verify CDP Packet Reception:

To confirm if the ESXi host is receiving CDP packets from the physical switch:

• Connect to the ESXi host via SSH.
• Run the following command (replace [xx] with the vmnic ID, e.g., vmnic0): vim-cmd hostsvc/net/query_networkhint --pnic-name=vmnic[xx]
• Review the connectedSwitchPort section of the output. If it is null, coordinate with the network team to ensure the physical switch is advertising CDP

Additional Information

For additional details related to Switch Discovery Protocols refer vSphere Documentation