I was interested in adding the one-click install for phpbb forum to my site. I have been to a number of sites that use forum.sitename.com to distinguish the forum from the rest of the site (as opposed to www.sitename.com/forum). Regarding the practice of putting the forum in a dedicated subdomain: Is this optional, best practice, or required by the forum itself. I’m not really afraid of running out of subdomains, but I understand that good planning ahead of time can save headaches later…
It’s become something of a convention lately, but the only real reason to use a new hostname for a forum is for ease of load balancing. If you have a high traffic site you can more easily move the forums to another server to distribute the load. It certainly isn’t required by the software (and any software that would require something like that is broken and should be avoided).
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