VMWare has made CDP (Cisco Discovery Protocol ) available to their host.

When you the CDP is running on router/switch where the physical network card is connected it provide information to both Network administrator and ESX admin about host name/network card. This information help when you are trying to figure out which network card on the host is connected to which physical switch

B|–set-cdp          Set the CDP status for a given virtual switch.
                        To set pass one of “down”, “listen”, “advertise”, “both”

On this ESX host we got 3 vSwitches, you need to enable the CDP feature for each vSwitch like (putty or console):

[root@ESX-vm2 root]# esxcfg-vswitch -B both vSwitch0
[root@ESX-vm2 root]# esxcfg-vswitch -B both vSwitch1
[root@ESX-vm2 root]# esxcfg-vswitch -B both vSwitch2

Now in vCenter 2.5 you see the Configuration > Networking > vSwitches, in te little comment box you can click:

This is the old result:                                                     This is the new CDP result:

More information: VMware