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'm looking to build a series of VMWare Virtual Machines as my client needs them.

The hostnames and IPs have been pre-assigned. But I'm going to need to add rules to our switches for each host's MAC address.

I'm trying to find out if I can predict the MAC addresses that are going to be generated.

share|improve this question
    
Out of curiosity, why add rules to the switches? Security policy or something else? –  Jed Daniels Nov 22 '10 at 23:02
    
Yeah, only known mac addresses inside specific networks can communicate outside of that network. –  St. John Johnson Nov 22 '10 at 23:26
    
I have no knowledge of how VMWare generates MAC addresses but I do know that security by MAC address is an absolute nightmare and massively prone to error. I can't think of a single circumstance when this would be preferable to using ACLs on the router. –  blankabout Apr 22 '11 at 6:34
add comment

3 Answers

up vote 4 down vote accepted

You can hard code them in a VM, but you can't predict them if you allow vmware to auto-generate them. VMware has a lot of different KB articles that mention this topic, but I think this one is the best place to start.

Some things to keep in mind:

  1. If you statically assign them, you must use the allowed range that VMware defines.

  2. If you replicate/copy/duplicate a VM that has a static assignment, you will have problems if it is on the same broadcast domain.

share|improve this answer
1  
As I'm sure @Jed knows, that should be broadcast domain, not collision domain. –  blankabout Apr 22 '11 at 4:48
    
@blankabout Thanks! Yea, I do know better, but I wasn't really paying attention. So noted, and corrected. +1 on the comment. –  Jed Daniels Apr 22 '11 at 6:08
add comment

You can set a static MAC by following the instructions in this link. That should give you all the control you're looking for.

share|improve this answer
add comment

Another thing to keep in mind is that the static MACs can be fragile. I can't remember the exact situations, but upgrading the guest's tools, changing the vNIC type, or doing a VMWare Convert could trigger the MAC address to change.

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.