I'm running into a very strange issue with my work network. About two months ago we migrated all of our domain controllers to server 2012 R2. Everything has been running perfectly fine until recently.
Our current setup involves two Dell R720 Windows Server 2012 R2 Hyper-V hosts, each host has a DC Virtual Machine. DC1 is on VHOST1 and DC2 is on VHOST2.
On the weekend of the September 27th, we ran into a problem with the NIC card on VHost1. Four days in a row, the host lost all connections to the network. We eventually moved the servers network connection to a separate PCI network card and that solved that problem. I'm unsure of this is related to the issue but I want to mention in case it's potentially part of the problem.
Unfortunately since Sunday morning we've been running into some bizarre issues. On Sunday morning, one of our servers completely stopped wanting to authenticate with the active directory. Every password I tried gave back the error "Username or password is incorrect" even though the username/pass combination was 100% correct and it worked on other machines. A restart of that server fixed the problem and authentication started working again.
Yesterday morning, DC1 started doing the same thing. No matter what credentials I gave it, it told me they were wrong. I restarted DC1, and again, the problem went away and authentication succeeded once again.
Last night, another server (different than the other two) stopped authenticating like the others did. Luckily I was able to use local credentials to get into the server restart it. Once again, restart fixed the problem.
I've checked the event logs and everything looks 100% fine except my failed logins. I've attached a few examples of what might point out a problem. But the errors in the event logs are very uncommon. The error about replication problems is only about once or twice a day, which I don't personally see as the problem.
DCDiag shows only one problem but it seems unrelated to the issue:
Starting test: FrsEvent
There are warning or error events within the last 24 hours after the
SYSVOL has been shared. Failing SYSVOL replication problems may cause
Group Policy problems.
I've attached the log from dcdiag as well.
Replication seems to be operating smoothly between the two DC's.
I'm very confused as to what could be causing these problems.
Anyone have any ideas? Have you run into these problems before?
Any help would be much appreciated.