subdomain not adding www. to dns same in vhost

[elftidus]

in vhost, sentora only adds this
ServerName forum.mydomain.com

but it doz not add
ServerAlias www.forum.mydomain.com

is there a way to add www. for sub domains? cant seem to see sub domain DNS settings in the DNS Manager of sentora.
i do have www.forum.mydomain.com setup on my godaddy DNS

How can i fix this ?

[Me.B]

add anotehr subdomain same root www.forum.mydomain.com that would do the trick.

M B

[apinto]

I'm not saying there are no use cases to use www. with a sub domain, there are good reasons to do it.
However it should not be a default, in your case the best option is like Me.B said, add another subdomain