Using a CNAME record with www

Question

We've had some issues with our domain provider (1&1) automatically resetting our CNAME record for a subdomain (which is www.).

I've spoken to them about this and they say they're resetting it because it's "inadvisable" to have a CNAME on a www subdomain, stating that Tim Berners Lee designed it to only be used with the root. This is news to me. As I understand it, there is nothing special about the www subdomain in a technological sense.

It may be unusual, but in our case its use with a CNAME is very deliberate. Is it actually breaking some technological best practice?

Answer 1

Barring unusual behavior from a web-browser or poorly coded application, there's nothing special about the www domain. I would suggest looking for a new DNS provider if they're willing to change DNS records without your approval or your knowledge.

Answer 2

If they're setting it to the same IP as the domain's main A or AAAA record, this may just be a kludgy attempt at CNAME flattening. If they're parking it or setting it to a different end IP, then that's clear abuse.

For what it's worth, lots of sites use www CNAMEs pointing to the @ A record. cPanel actually usually sets that by default, so you only have to update your @ A or @ AAAA record once. And given the amount of caching present in DNS, there's not a real, tangible performance tax or benefit being incurred here unless you have a particularly bad DNS implementation.

Reality is that, CNAME or not, you're eventually ending up with an IP address, and it will end up being cached somewhere. So I recommend finding a DNS vendor that doesn't try meddling with your records for some holier-than-thou reason.

-Mike