I have a interesting yet very annoying problem. The server setup: Server 1: Win2k3 - As domain controller with global catalog Server 2: VMWare ESX with a Win2k8 R2 VM that has only Exchange 2010 installed on it. Also a Win2k3 VM that has other misc software. Both physical servers tied to same switch. There are other servers but this is all that is needed to be relevant to the problem. The issue: At random it seems the exchange 2010 and domain controller can not ping each other. Yet at the same time of this they can ping the Win2k3 VM and the internet servers. The event seems to last about 10 minutes each time and seems to occur anywhere from two hours to 12 hours apart. First go around, I checked ARP, both servers dropped off in each others arp entries. I made them static assignments, problem persists. Granted this might be a byproduct of what ever is causing the issue as I might have checked arp after the 5 minute timeout. Second go around, I checked ARP on the switch about two minutes after it started, ARP for both servers exists in its tables. Third go around, before it occurred I threw all security out the window, firewalls are off on both servers, event still occurs. Forth go around, I did a packet capture of the ending of the event and did not observe anything out of normal network traffic. I am now out of ideas as to what this could be, looking for help/ideas.