This is bit of a theological question, but nonetheless...

So, a server has a hostname, let's say the fqdn is hostname.example.com (to be really precise about what I mean, this is the name that is set in /etc/sysconfig/network).

The very same server has multiple interfaces on different subnets. Let's say the IPs are 10.0.0.1 and 10.0.1.1.

Now the question is, is it theoretically (mind you, this is important, I know that practically it works, but I'm interested in purely academic answer) allowed to have the following setup:

interface1.example.com. IN A 10.0.0.1
interface2.example.com. IN A 10.0.1.1
hostname.example.com. IN CNAME interface1.example.com.

OR should it rather be:

hostname.example.com. IN A 10.0.0.1
interface2.example.com. IN A 10.0.1.1
interface1.example.com. IN CNAME hostname.example.com.

I guess it's obvious which one is making more sense from the management/administration POV, but is it technically correct?

The argument against the first setup is that a reverse lookup to 10.0.0.1 returns interface1.example.com and not what one might expect (ie the hostname: hostname.example.com), so the forward request and then sub sequential reverse lookups would return different results.

Now, as I said, I want a theoretical answer. Links to RFC sections etc, that explicitly allows or disallows use of CNAME name as a hostname. If there's none, that's fine too, I just need to confirm. I failed to find any explicit statements so far, bar this book, where this situation is given as an example and implies that it can be done as one of the ways to avoid MX records pointing to a CNAME.