How to set forum under maintenance?
If you are going to perform global website changes or you would like to temporary disable your forum you can achieve this via the vBulletin administrative panel by referring to the vBulletin Options menu. From the settings list, please click on the Turn your vBulletin on and off and click on the Edit Settings button.
On the new page set the Forum Active directive to No and apply your Reason For Turning Forum Off – be advised that this is the message that will be displayed to your visitors when they access your forum.
You can proceed by clicking on the Save button on the bottom of the page.