Vodder
Enthusiast
Enthusiast

MAC address OUI confusion

Hi,

I always thought that MAC addresses assigned by ESX were of the format 00:50:56:XX:XX:XX and still is as confirmed here

http://pubs.vmware.com/vsphere-esxi-4-1-installable/wwhelp/wwhimpl/js/html/wwhelp.htm#href=server_co...

However when trying to hunt down some particular weird happenings on a DC; whilst in the ARP cache I noticed a lot of 00:0c:29:XX:XX:XX addresses. By chance I then noticed these were linked to a group VM's on a stand alone host.

These haven't been manually changed and I was expecting 00:50:56:XX:XX:XX. Googling around I found nothing direct from VMware on this, however I did find a blog that stated the 00:0c:29:XX:XX:XX range is used when a VM is created directly on an ESXi host. Is this true? These VM's were not created directly on any host however they were manually added to the inventory of the standalone host - would this cause this?

In addition the blog also mentioned the OUI 00:05:69 as potentially being used by VMware.

Can any clarify this please?

Thanks.

Tim

@timgleed | VCAP5-DCA/DCD | VCAP4-DCA/DCD | VCP5 | VCP4 | VCP3 | VCP4-DT | VCA4-DT | VTSP4 | MCITP | PRINCE2 | ITIL | BSc Hons
0 Kudos
4 Replies
Vodder
Enthusiast
Enthusiast

OK, according to http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&externalId=219&sliceI...

Automatically generated MACs are 00:05:69 and manually generated ones are 00:50:56. However none of these VM's were manually generated and never have been, what constitues an automatically generated MAC address?

No mentioned of 00:0c:29 either

@timgleed | VCAP5-DCA/DCD | VCAP4-DCA/DCD | VCP5 | VCP4 | VCP3 | VCP4-DT | VCA4-DT | VTSP4 | MCITP | PRINCE2 | ITIL | BSc Hons
0 Kudos
AndreTheGiant
Immortal
Immortal

Have a look at:

http://communities.vmware.com/thread/7365

Andre | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro
0 Kudos
Vodder
Enthusiast
Enthusiast

Thanks! Not sure why that didn't come up in my searches.

Do you know when does the UUID algorithm comes into play over the "old" algorithm? I have VM's created today on ESXi 4.1, HW version 7, and their MACs are in the 00:50:56 range. They were not manually assigned either.

@timgleed | VCAP5-DCA/DCD | VCAP4-DCA/DCD | VCP5 | VCP4 | VCP3 | VCP4-DT | VCA4-DT | VTSP4 | MCITP | PRINCE2 | ITIL | BSc Hons
0 Kudos
bedickson
VMware Employee
VMware Employee

Vodder,  I had similar questions and after some digging I cobbled together the folowing info:

VMware has four OUI for MAC addresses

00:0C:29 (Used when auto-generating a MAC for a VM created directly on an ESXi host)

00:50:56 (Used for vCenter generated & static MAC addresses)

00:05:69 (Used for auto-generated MACs on ESX 1.0 - 2.5)

00-1C-14 (I’m not sure what they are doing or going to do with this one)

The static and vCenter generated MACs don’t overlap because the static range ends at 00:50:56:3F:FF:FF and the vCenter generated range starts with 00:50:56:80:00:00 which is always greater than 00:50:56:3F:FF:FF.

I believe the algorithm vCenter uses is 00:50:56:(80+ vCenter ID#):XX:XX where 80 is Hex and the vCenter ID is a Dec number between 0 and 63  automatically generated when vCenter is installed but it can be changed manually.  The last two bytes are generated based on a hash of the VM name

For instance a VM has a MAC 00:50:56:8A:00:2D so we know that it was set automatically by vCenter because it is higher than 00:50:56:3F:00:00 and the vCenter ID is 10 because the 4th byte is 8A  and in Hex 8A-80=A which is 10 in Dec.

A VM generated on an ESX host uses the formula 00:0C:29: (SMBIOS UUID of host):(Hash of  VM name)

I hope that helps.

0 Kudos