Windows – Slow DNS Resolution with Windows

If your Active Directory domain name is "mydomain.com" and you have an externally hosted website called "www.mydomain.com" you would have to (as you said) create an "A Record" on your internal Windows 2008 DNS server pointing to the IP address of the external webserver.

A better method would have been to call your Active Directory domain "mydomain.local" or "ad.mydomain.com" and let an external DNS server be authorative for "mydomain.com".

From your other post I see you are using SBS 2008. Unfortunately you cannot rename the AD domain name without reinstalling SBS 2008 from scratch.

Edit.

if you are talking about true "sub domains" then you could create the subdomain on your external DNS server, and internally on the Windows DNS server you can delegate authority to the external Nameserver.

For example a subdomain called "newyork.mydomain.com" could have hosts called "www.newyork.mydomain.com" and "ftp.newyork.mydomain.com" etc.

But I think in your case you are referring to hostnames rather than subdomains. Which means you will need to create an "A record" for each external hostname.

This is not directly a DNS problem, it's a network routing problem between some parts of the internet and the DNS servers for serverfault.com. Since the nameservers can't be reached the domain stops resolving.

As far as I can tell the routing problem is on the (Global Crossing?) router with IP address 204.245.39.50.

As shown by @radius, packets to ns52 (as used by stackoverflow.com) pass from here to 208.109.115.121 and from there work correctly. However packets to ns22 go instead to 208.109.115.201.

Since those two addresses are both in the same /24 and the corresponding BGP announcement is also for a /24 this shouldn't happen.

I've done traceroutes via my network which ultimately uses MFN Above.net instead of Global Crossing to get to GoDaddy and there's no sign of any routing trickery below the /24 level - both name servers have identical traceroutes from here.

The only times I've ever seen something like this it was broken Cisco Express Forwarding (CEF). This is a hardware level cache used to accelerate packet routing. Unfortunately just occasionally it gets out of sync with the real routing table, and tries to forward packets via the wrong interface. CEF entries can go down to the /32 level even if the underlying routing table entry is for a /24. It's tricky to find these sorts of problems, but once identified they're normally easy to fix.

I've e-mailed GC and also tried to speak to them, but they won't create a ticket for non-customers. If any of you are a customer of GC, please try and report this...

UPDATE at 10:38 UTC As Jeff has noted the problem has now cleared. Traceroutes to both servers mentioned above now go via the 208.109.115.121 next hop.