Dynamic DNS and cnames

Kevin Darcy kcd at daimlerchrysler.com
Tue Aug 5 21:41:15 UTC 2003


Ladislav Vobr wrote:

> We are having customers with dynamic ip addresses running their services
> on dynamic IP addresses. We don't offer dynamic dns updates. Is there
> any other way customer can update his dns. The problem is like this.
> Customer has set up dynamic DNS service with some other DNS provider,
> having for example mail.dyn-dns.org be his mailserver and
> www.dyn-dns.org to be his web. My question is - on our dns servers
> customer has for example testdomain.ae configured  and he wants
> www.testdomain.ae and testdomain.ae to be a cname to his
> www.dyn-dns.org and mx record to be a cname to his mail.dyn-dns.org. As
> I know having cname for domain is not possible and having cname in MX
> record is not  correct as well, any way how to achieve this ?

No, the name of a zone cannot legally own a CNAME record, nor is it legal
for the target of an MX record to be a CNAME. This "illegality" is not some
artificial constraint either: if you break these rules the results will be
unpredictable and can be rather difficult to troubleshoot. Just Don't Do
It.

Your customer's only reasonable choice is to have A records for the
zone-apex and MX target which are updated in parallel with the dyn-dns.org
updates.


- Kevin




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