I'm trying to join a Windows Server 2003 R2 guest to a domain with a Windows Server 2012 R2 Domain controller server. I get the error "The following error occured attempting to join the domain "mydomain.local" the specified network name is no longer available." DNS is ok I can do nslookup just fine. I cannot access the SYSVOL or NETLOGON from the 2003R2 server, I get the same error "network name is no longer availalbe". I've disabled AV / Firewall on the domain controllers and the 2003 R2 guest. The domain functional level is "2008 R2". Is this setup not supported or does anyone know what I'm doing wrong?
EDIT: This is a new domain set up for test purposes. I successfully joined a 2008 R2 server and another 2012 R2 already.