I have a Server 2003 network with a single domain controller (it has a static IP, is running DNS, and the Primary DNS Server is pointed to 127.0.0.1). Everything worked fine. I then added a Server 2012 Essentials machine and created a second, different domain on the same physical network. I made it a DC as well, installed DNS, gave it a static IP and pointed the Primary DNS Server to itself as well. The setup was completely automated, no problem. The only thing I needed to do was to set up a Trust Relationship between the old and new DCs, which I did. It was a 2-way, External trust, not transitive, and it verified perfectly from both ends. Users logged into the new domain could access resources on the old domain (e.g. file shares, etc.). No problems.
This morning I wake up and all of a sudden the new domain users can't access shares on the old DC. I tried to check the trusts from AD Domains and Trusts on the new DC and I can verify the OUTGOING trust, but not the incoming one, I get the "No Logon Servers Available..." message. Now the old domain controller can't find the new domain controller. The only thing that happened overnight was, I believe, that the new DC (Server 2012) rebooted to install updates. I've driven myself crazy trying to figure out what the problem could be. As I say, when I initially set up the trust it went like a breeze. All of a sudden, "No Logon Servers Available..." when trying to Validate, from the new DC, the incoming trust.
BTW: I've disabled the firewalls, all to no effect. I CAN ping the new DC from the old DC, both by IP and computer name.
Any pointers as to what to check or where to look would be greatly appreciated.
Edit: I just used Windows Explorer, on the old DC, to browse the new domain. After a while the new domain appeared with all its computers. I was then able to add the two way trust with no problems, it validated fine. Unfortunately, the next time I tried to validate the trust I got another error message: "the local security authority is unable to obtain an rpc connection to the active directory...". This is driving me crazy!
Again, thanks in advance for any pointers.