For the past 5 months we have been having a strange issue on our new server (less than a year old). The server in question is running SBS 2011 and acts as our DC.
The issue: Every so often the server will completely lose all network connectivity. No workstations can communicate with it and it itself cannot communicate with any of the workstations, or the internet. Any attempt to change or disable/enable the NIC results in the process just hanging until a reboot.
The band-aid "fix": So far the only way I've been able to restore connectivity is to reboot the server.
The details: The strange thing about this is that it almost always happens on the weekend. Usually sometime between Saturday nights and Sunday mornings (only once has it happened on a weekday, a Monday). I'm not super knowledgeable when it comes to servers, so we've had an outside IT company come in twice now. Both times they've told us they can't figure out what's wrong, they don't see any issues. The first time I discovered that the server has two NICs so I simply plugged in and set up the other one (unplugged the original one). And it worked, we didn't experience an outage that next weekend. At this point we assumed it had to be hardware related. I figured since the server is under warranty we might as well get the motherboard replaced.
So DELL sends some one out to replace the motherboard. Everything is working good. Two weeks later we have another outage, same symptoms, same temporary fix. That's when we had our outside IT company come in for the second time, again, no solution, no diagnosis. So I plug in the other NIC card on the new motherboard. No outage the next weekend. But this weekend we had an outage again. It had gone 12 days without one, so it broke the pattern, leaving me more confused.
If it was hardware related I don't understand why it would happen on such a regular basis. And I can't for the life of me find anything software related that would cause this either. Is there anyone that could shed any light at all on this?
- We've tried reinstalling, updating, and rolling back NIC drivers
- Event log isn't showing any issues for the time when connection was lost
- We've checked for any scheduled tasks that might be causing an issue, no tasks are schedule for Saturday nights or Sunday mornings
- Workstations still have internet connectivity (going through an alternate DNS) so our switch, modem, and firewall all seem to be working fine.