Ref link; kb.vmware.com/kb/1003885

To configure the ESX host:

1.Log in as root to the Service Console (via SSH, remote console, or physical console).


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

[root@server root]# esxcfg-vswitch -b vSwitch1
down

The output of down indicates CDP is currently not implemented.


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

[root@server root]# esxcfg-vswitch -B both vSwitch1


4.Verify the new setting:

[root@server root]# esxcfg-vswitch -b vSwitch1
both
The following is an example of configuring CDP for a Cisco 6500 physical switch:
1.switch#
2.switch# config terminal
3.switch(config)# cdp run
4.switch(config)# interface g1/1
5.switch(config-if)# cdp enable
6.switch# show cdp neighbors

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
pa-tse-h24.pasl.vmware.com Gig 1/1 121 S VMware ESXvmnic2
pa-tse-h24.pasl.vmware.com Gig 1/2 121 S VMware ESXvmnic3