I'm struggling to setup an additional subdomain as a parked domain on my wordpress install. It's a relatively trivial thing I want to do but I have my reasons - I'm hoping someone can help me out.

Let's assume I own mydomain, I can reach my wordpress site by visiting mydomain and www.mydomain

What if I also want aaa.mydomain to resolve to the same wordpress site, what's the correct way to achieve this? I've tried a CNAME record resolving to mydomain and I've also parked aaa.mydomain and used an A record but both return a 404 error.

Any thoughts?