There may be times where you want to host a subdomain on a different server than the main domain. To accomplish this, you need an A record, added either at the domain registrar if possible, or the server that hosts mydomain.com.
sub.mydomain.com. 14400 IN A XXX.XXX.XXX
The X’s should be replaced by the target server’s IP address. I prefer changing this info at the domain record level, since that doesn’t require cooperation of the main domain’s host, and thus can be changed by the domain owner in the event the target server’s IP changes.
For this to work, the subdomain MUST be added to the target server. A very simple way to do this is to add the main domain as an Addon in cPanel, and then set up the subdomain which will add all the relevant DNS entries (even though the main domain is not actually hosted on the target server). ((Caveat – I’ve found you may see occasional weirdness, though, with the approach described, such as a WordPress installation that requires uploads to go straight to the upload folder to work, instead of month and year-based folder settings. Would probably be better to add the subdomain to your server configuration directly for long-term robustness.))
