Does the vMAC address change when VMotioned?

[bigusdadius]

When a VM is vmotioned, does the virtual MAC address change?

[hicksj]

Not that I've seen.

That would cause problems, I'd think for folks that use MAC based network security.

[MR-T]

If MAC address changes could cause you issues, it's worth considering static entries.

This way, your vm's will not recieve different MAC's when config changes occur.

http://kb.vmware.com/vmtnkb/search.do?cmd=displayKC&docType=kc&externalId=507&sliceId=SAL_Public

[esiebert7625]

If it's a Windows VM you can also enter any MAC address you want for your virtual NIC as long as it has valid hex numbers. Just go into the properties of the NIC in Windows and under Advanced, Network Address put in a MAC address, for example. 00-00-1B-AD-BA-BE

[DLevine]

The vMAC address is defined in the VM's vmx file (config file), so it remains consistent when it is vmotioned.

You can specify custom mac addresses for your VM's a few ways - but you will have to be sure it is allowed on your vSwitch or port group...

[chrisbuzby · Accepted solution]

Your MAC is figured out during "startup" via an algorithm based on a hash of the path to the vmx file and the uuid of the esx server (if created via VC it also takes into account the uuid of the VC Server), that being said when you vmotion the MAC does not change... You can hardset the MAC in the vmx file as well to ensure it never changes. Also a virtual machine restart does not kickoff the algorythm according to my instructor you will opssibly have to stop the server completly and restart...

[bigusdadius]

Thanks to all that replied, the actual reason I asked is that a customer I currently working with wants an inventory of all MAC addresses physical and virtual and I wanted to ensure the data was old as soon as I printed it...! Thanks again.