Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

I want to assign my virtual machines MAC addresses so that I can configure DHCP reservations for them so that they always get the same IP address regardless of which host hypervisor they are running on or operating system they are running.

What I need to know is what range of MAC addresses can I use without fear that one day some device may be connected to our network with that MAC?

I have read the Wikipedia article on MAC addresses and this section seems to indicate that if I create an address with the form 02-XX-XX-XX-XX-XX then it is considered a locally administered address.

I would assume this means that no hardware manufacturer would ever use an address starting with 02 so I should be safe to use anything that starts with 02 for my virtual machines?

Thanks for the help.

share|improve this question
add comment

4 Answers 4

up vote 39 down vote accepted

There are actually 4 sets of Locally Administered Address Ranges that can be used on your network without fear of conflict, assuming no one else has assigned these on your network:

x2-xx-xx-xx-xx-xx
x6-xx-xx-xx-xx-xx
xA-xx-xx-xx-xx-xx
xE-xx-xx-xx-xx-xx

Replacing x with any hex value.

share|improve this answer
5  
Useful translation of the wikipedia version: "Universally administered and locally administered addresses are distinguished by setting the second least significant bit of the most significant byte of the address. If the bit is 0, the address is universally administered. If it is 1, the address is locally administered. In the example address 02-00-00-00-00-01 the most significant byte is 02h. The binary is 00000010 and the second least significant bit is 1. Therefore, it is a locally administered address.[3] The bit is 0 in all OUIs." –  Adam Brand Jul 14 '09 at 21:11
add comment

The complete list of assigned mac prefixes can be found here: http://standards.ieee.org/regauth/oui/oui.txt

There are several prefixes marked private on that list, 02 is not one of them. If you use one of those, you should be relatively safe. Keep in mind that other devices, software, etc. may also use that prefix, in which case your chance of a conflict goes up slightly.

If you are using randomly generated suffixes, your odds of collision are pretty astronomical.

share|improve this answer
    
The IEEE only lists public OUIs. A much more exhaustive list can be found at anonsvn.wireshark.org/wireshark/trunk/manuf among other places. The comments about locally administered addresses are otherwise correct. If you really care about such things you could take an existing VM-related OUI, e.g. VMWare's 00:05:69 and make it locally administered: 02:05:69. –  Gerald Combs Jul 14 '09 at 21:27
    
I have seen this list but given that those listed as private may still conceivably end up on our network I wanted to find an a range of MACs that were explicitly not going to be used by any company. –  Chris Magnuson Jul 14 '09 at 21:34
    
Just keep in mind that "complete" lists have a habit of becoming incomplete rather quickly within the IT industry. –  John Gardeniers Jul 15 '09 at 2:39
    
As of 20121031, standards.ieee.org is not responding. –  retracile Oct 31 '12 at 16:19
    
Of course the LAA ranges are not listed in there. They aren't managed by the IEEE (or in fact anyone). –  Falcon Momot Jun 13 at 22:17
add comment

Are you using VMware? If so the range set up by VMWare for manually applied MAC addresses is 00:50:56:00:00:00-00:50:56:3F:FF:FF

share|improve this answer
    
We are using Hyper V. Interesting to note that VMWare specifically carves out a range of its MAC addresses for manually assigned MACs. Thank you for the info. –  Chris Magnuson Jul 14 '09 at 21:29
add comment

For Xen virtual machines you can use anything starting with 00:16:3E, and that's the default which many management tools will generate.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.