DNS Issues with Server 2008 R2

RFC 2671.  This shouldn’t mean much of anything to most of us. This RFC Code, however, can literally mean hours and hours of frustration and troubleshooting if you have created a Server 2008 R2 domain.

Developed in 1999, Extension mechanisms for DNS aka eDNS, were designed to allow for increased functionality of the DNS protocol. They were also critical to the implementation of DNS Security Extensions (DNSSEC). Nevertheless, the protocol hasn’t really caught on and there are still thousands of devices – even ones produced today – that are not really fully compliant with the standards laid out in RFC 2671.

Naturally, the Internet itself is a inter-connected network that is literally running on loads of old and obsolete equipment.  So, it comes as no surprise that there are going to be a few problems arising from the fact that Windows Server 2008 R2, when set up as a DC with the DNS role installed and set to perform recursive lookups, has this extension to DNS enabled by default.

Not everyone, fortunately, will have issues with this as there are of course DNS servers out there that will respond properly to this type of query and respond with the IP address requested. However, if you happen to be running DNS queries against one that is non-compliant, you will end up with extremely patchy Internet service for your whole domain.

To check if this is an issue for your domain, you are going to have to run a few tests.

Open network monitor, and look at the DNS queries that you are getting. If they look like the picture below, you are probably encountering this issue.

dnserror

The fix, luckily, is very simple.  Simply disable eDNS and re-enable it at some point in the future when acceptance of this protocol is a little higher.

Open up a cmd prompt and elevate it (right click on it and run it as an administrator). Then run the following command.

dnscmd /config /EnableEDNSProbes 0

This should take effect immediately.

I sincerely hope that this helps a few of you out there that are just starting to deploy Server 2008 R2 now that SP1 is out.

Cheers!

Matt

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Copyright © 2010 Paul Guenette and Matthew Sleno.