Podcast Settings 
The Podcast Settings (Forums & Moderators > Forum Manager > Podcast Settings) section allows you to configure iTunes specific settings for your forums.

Podcast feeds will work inside of iTunes (and other aggregates that support enclosures) without any information on this page being filled in. These settings are used when you wish to submit one of your forums as a podcast to iTunes as a podcast that can be searched for and seen from within iTunes.

Warning:
There are several caveats that you must be aware of for this process to be successful.
Requirements:
  1. vBulletin Options > External Data Provider > Enable RSS Syndication must be enabled.
  2. vBulletin Options > External Data Provider > Enable Podcasting must be enabled.
  3. The forum in question must be viewable by guests.
  4. You must set Enabled to Yes and select a Category.
  5. The feed to your podcast must be called with the forumid of the forum. You can not combine multiple forums into a podcast that includes iTunes specific information.
    Ex: http://www.example.com/forums/external.php?forumids=2
  6. iTunes only support six filetypes: .m4a, .m4v, .mp3, .mp4, .mov, and .pdf
There are two options to add the enclosure to the podcast. The first option is to add an attachment to the first post of the thread. This option is limited in that:
  1. Attachments in the forum must be viewable by guests.
  2. Due to the decision of Apple to limit valid enclosure urls to those that end with the extensions listed above, podcasting via iTunes will not work on IIS servers and possibly others. If you need help verifying that podcasting will work on your server, please contact vBulletin support. Hopefully, Apple will come to realize that there are better ways to determine valid urls and will lift this restriction in the future.
The second option is to enter a URL in the Podcast URL field when submitting a new thread in the podcast forum.
User Contributed Notes: Podcast Settings Add a Comment