VM /ETC

Let’s say you need to quickly figure out if a remote server is a VMware virtual machine (VM). I won’t go into reasons why you might not already know, or why you would need to know, but let’s just say you do. If you have Remote Desktop access you can check the hardware devices, but what if you can’t and you need to tell remotely? I can’t think of an easier indicator than the server’s MAC address.

When ESX Server automatically generates a MAC address, the first three bytes are the VMware Organizationally Unique Identifier, or OUI. ESX Server uses one of two VMware OUIs for network adapters:

• If you initiate the virtual machine directly in ESX Server, ESX Server uses 00:0C:29:XX:XX:XX
  
• If you initiate the virtual machine in VirtualCenter, ESX Server uses 00:50:56:XX:XX:XX

If I am not mistaken the VirtualCenter generated MAC OUI is also the same for VMware Workstation, Fusion, and Server, but don’t hold me to that.

Armed with knowledge of the standard OUIs, it’s now easy to tell a VMware VM by the MAC address.

To get the remote MAC address using a Windows XP or Vista desktop, for example, enter the following at a command prompt:

>getmac /s [servername or ip] /u [domain\usename]
As an example, I know my lab VirtualCenter (VC) is a VM. Here’s a screen shot of using getmac from my Vista notebook. Note that I am prompted for the password, but I could have included it in the command with a “/p” switch. You still need administrative access on the remote server.

The OUI is 00:OC:29. Makes sense that the VC VM was generated from an ESX server, right? Otherwise, this example would have been a “twilight zone”, “how did that happen?” scenario. J

You may be thinking what about pinging the remote server and then using the ARP command ( >arp –a ). to view your updated ARP cache? That will work if you are on the same ip subnet as the other server, but if not, MAC addresses do not route and ARP does not work.

I am not aware of an equal tool to getmac in Linux. Fill me in if you know of one.

Another option could be to use PsExec or Putty for a remote console session, then use ipconfig /all or ifconfig to get MAC addresses.

I guess if you have access to the switches you could get the MACs that way too.

Let me know if you have a foolproof, easier way to determine a VMware VM remotely

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