Fix Slow External DNS Resolution in Microsoft/Active Directory DNS Server
Recently, we found that one of our DNS servers was resolving external hostnames unacceptably slow -- about 5 seconds, give or take. The resolution was so slow, in fact, that all of the clients hopped on to the secondary DNS server thinking that the primary had gone down. After logging on to the server to troubleshoot, I could see that: 1. Pinging external hostnames worked well after the hostname resolved. So did traceroute. 2. Caching wasn't working at all 2. Other AD DNS servers on the network were resolving external hostnames quickly 3. The root servers were all there but I deleted and reloaded them anyway - Note: you can actually load root servers from a root server which is cool 4. Internal hostname resolution was extremely fast 5. A reboot didn't help (you may laugh but this has solved severe AD problems for me) Because the other AD Servers were picking up the slack, I decided to come back to it later. I went out and had dinner with a friend then returned after a few h...