To configure CDP for a Standard vSwitch:

Log in as root to the Service Console (via SSH, remote console, or physical console if connecting to ESX) or to management vmkernel port (if connecting to ESXi).

Verify the current CDP setting for the desired virtual switch (vSwitch1, in this example):

esxcfg-vswitch -b vSwitch1

You see an output similar to:

listen

The output of listen indicates CDP is configured to read CDP information from the physical switch if available.
This is the default setting for ESX/ESXi 3.5, 4.x, and 5.x.

Set the CDP status for a given virtual switch. Possible values here are down, listen, advertise or both.

• Listen mode – The ESXi/ESX host detects and displays information about the associated Cisco switch port, but information about the vSwitch is not available to the Cisco switch administrator.
• Advertise mode – The ESXi/ESX host makes information about the vSwitch available to the Cisco switch administrator, but does not detect and displays information about the Cisco switch.
• Both mode – The ESXi/ESX host detects and displays information about the associated Cisco switch and makes information about the vSwitch available to the Cisco switch administrator.

esxcfg-vswitch -B both vSwitch1

Verify the new setting:

esxcfg-vswitch -b vSwitch1

You see an output similar to:

both

Enable CDP with PowerShell

$esxcli = Get-EsxCli -VMHost $myhost
$esxcli.network.vswitch.standard.set("both","1500","vSwitch0")

To configure CDP on a vNetwork Distributed Switches (vDS):

1. Connect to vCenter Server using the vSphere Client.
2. In the vCenter Server home page, click Networking.
3. Right-click the vDS and click Edit Settings.
4. Select Advanced under Properties.
5. Using the checkbox and the dropdown, change the CDP settings.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003885