Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Just want to know if it's true that if you use the VLAN ID 4095 for guest VLAN tagging, then vMotion will not work correctly as there is nowhere to pass back the reverse arp to? So, the problem we have noticed is when we have vmotioned VM's that are tagged on our trunk network, you cannot ping them from anywhere between 30-300 seconds. The hosts don't know which VLAN the guest is on.

Is this right and also the correct behaviour?


share|improve this question

Certainly it's true that, depending on how your networks are setup, you can have problems when using 4095 for VGT but that masks an entirely different problem I can see with your system - why are you using one vswitch for both vmkernel and VM traffic? I know it may well work for you but it's not recommended in any way due to the problems you will encounter, one of which you've hit already.

Separate your vmkernel and VM traffic vswitches/ports as you're supposed to.

share|improve this answer
So if I separate the traffic then I can get this working? i.e. we want to use guest VLAN tagging and be able to use vmotion without any downtime. – user121282 Jun 18 '12 at 14:43
Well it should work as it is, but you're supposed to use a separate vswitch for vmkernel traffic, if you did that then it wouldn't matter whether you use vlan 4095 on the VM traffic vswitch or not - vMotions would not be impacted. – Chopper3 Jun 18 '12 at 14:48
Sorry, I just checked and we do actually have a separate vswitch for vmkernel traffic. – user121282 Jun 18 '12 at 14:54
In that case the use of 4095 is irrelevant. – Chopper3 Jun 18 '12 at 14:55
Why, how else am I going to use virtual guest tagging? – user121282 Jun 18 '12 at 15:21

I have personally used this scenario more than once with great success. So no, this NOT true.

share|improve this answer

Your Answer


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.