I have a Windows Server 2012 Essentials server that has been up and running for a year. The Server is the domain controller with the DNS server role installed. There is only one NIC card used on the network. Today, DNS stopped working. The server and the clients can access internet websites if IP addresses are used; otherwise, accessing websites fails. Looking at the DNS properties page on the Forwarders tab, I see that each DNS server listed (which are the DNS servers given to me by my ISP provider) says <Unable to resolve>. When I saw that those addresses were not resolving, I added Open DNS IP addresses and I added google's DNS addresses in the DNS forwarders list but they too said <Unable to resolve>. I can ping the Open DNS IP addresses, the google DNS IP addresses and the ISP provider's DNS IP addresses. NOTES: 1) I tried unchecking IPv6 on the DNS' server's Ethernet adapter properties; 2) I have done a flushdns; 3) I have verified that my DNS services are running; 4) the first DNS on my server's Ethernet adapter properties is the IP address of the DNS server (which is 10.0.0.51) and the second is the loopback (127.0.0.1); 5) the power management on the NIC adapter is disabled; 6) nslookup works for 8.8.8.8 but not for www.google.com.
I removed the Forwarders and tried to use just Root Hints. That didn't make any difference. I went back into DNS Manager->[DNS server name]->right-click properties->select Root Hints tab. I clicked on a.root-servers.net to edit. Under the Validated column it says "a timeout occurred during validation". I clicked cancel to back out of everything I was doing.
As I mentioned, this was all working fine until this morning. Can someone tell my why the Forwarders are unable to resolve? An why the Root Hints timeout during validation?