The Only Thing Constant is Change
On January 29, 2004, the the IP address for the DNS root hint for b.root-servers.net changed to 18.104.22.168:
Copy from Server Doesn't Always Copy from Server
I was testing the DNS configuration on two Windows Server 2003 machines. One is R2 SP2; the other is SBS 2003 SP2. In the DNS server's properties, on the Root Hints tab, I clicked on the Copy from Server button and copied from 22.214.171.124 (a Level 3 DNS server). However, this did not update the address for b.root-servers.net; it still showed the old 126.96.36.199. So when I ran dcdiag /test:dns, it reported an error on accessing b.root-servers.net.
I tried removing b.root-servers.net and copying from 188.8.131.52. This time, b.root-servers.net showed up with IP Address “Unknown”. This is strange, since I can use nslookup against 184.108.40.206 and get the correct address for b.root-servers.net. Apparently 220.127.116.11 does not let you copy root hints, although no error is displayed.
Next I tried copying from my ISP's DNS server. This worked, but it did not replace the old IP address; it just added the new one.
The bottom line is that once you get your root hints set up, you'd better double-check them against the official list here.
Old DCDiag Raises False Alarms
Another “gotcha” I encountered is that the original DCDiag program in Windows Server 2003 Support Tools was telling me that all of my root hints were bad. Microsoft Support suggested updating to the SP2 version of Support Tools, which did in fact fix that problem.