Strange behaviour resolving CNAME's via a forwarder.

[Chris Buxton]

On Apr 20, 2011, at 2:19 AM, Adam Goodall wrote:
> However if a client queries server A  for mail.testdomain.com (type any) the request is not answered. From the logs on server B i can see that server A is only forwarding on a request of type A. As an A record for mail.testdomain.com does not exist on server B it does not resolve.
> 
> If i then specifically query Server A for mail.testdomain.com of type CNAME, it resolves as expected. Subsequent requests against server A for mail.testdomain.com of type any then resolve, presumably because it is already in the cache.
> 
> Hopefully that makes sense! Has anyone had a similar issue and did you come up with a work around? Is this expected behaviour or a bug?

This is an excellent example of why you should not forward to an auth-only server. Use a stub zone instead. You might need to give it an empty forwarders list, to override forwarding set in either the options or view statements.

For example:

zone "testdomain.com" {
	type stub;
	masters { 192.168.1.1; };
	forwarders { };
};

Try it, you'll like it.

Chris Buxton
BlueCat Networks

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