Em seu /etc/httpd/conf/httpd.conf
### Section 3: Virtual Hosts
NameVirtualHost *:80
<VirtualHost *:80>
ServerAdmin [email protected]
DocumentRoot /home/windshear-gaming.com/public_html/portal
ServerName windshear-gaming.com
ErrorLog logs/windshear-gaming.com-error_log
CustomLog logs/windshear-gaming.com-access_log common
</VirtualHost>
<VirtualHost *:80>
ServerAdmin [email protected]
DocumentRoot /home/windshear-gaming.com/public_html/forum
ServerName forum.windshear-gaming.com
ErrorLog logs/forum.windshear-gaming.com-error_log
CustomLog logs/forum.windshear-gaming.com-access_log common
</VirtualHost>
Isso atenderá seu domínio e subdomínio em cada IP que seu servidor da Web estiver escutando corretamente.