Citrix vs network?

Question

linux

Dear experts!
I want to ask for advice.
There is, then a situation that does not give rest. I hope there is a solution to the problem.
On one physical machine is Citrix XenServer. two gigabit network interfaces (intel).
one with other servers, the other for clients.
This hypervisor has several simultaneously running VMs (6 pcs in a small load).
4 pcs Centos 6.5, 1 pcs FreeBSD and WinXP.
A few months ago, there was a case
On the VM with Windows, the network disappeared. and suddenly and unexpectedly. It does not ping clients and the VM itself does not ping clients when everything is fine on the second interface. Then after a while, the network appears. and so on in a circle.
I noticed that the entry in the ARP table corresponding to this interface disappeared. There are no conflicting MAC addresses.
Since this VM was of no value and was only needed for experiments, it was destroyed with the thoughts that it was to blame for everything ...
So I thought until now, but, just yesterday, the case repeated itself and identically, but VM with Centos.
Biting my nails, I began to dig the Internet in search of an answer, but alas, I did not find anything.
One friend advised me to upgrade the hypervisor, but reading the changelog did not find anything related to a similar problem.
What should I do? Maybe someone faced a similar problem?
Thank you for your attention.

Answer 1

The answer has been found! some not a good person connected to the network and appropriated the address of the VM! Sabotage. it remains to find this scoundrel and punish him to the fullest extent of the law!

Answer 2

there is an assumption that this is the arp table
1. check the arp table on the VM.
2. check the arp table on the connecting switches (I had a problem after replacing the cables in places, when the Hp 1910 switch prescribed the old mac-address for the interface)