fallback controller

[eluser]furnissg[/eluser]
Hi, im new to CI and looking for a way to speed up my development. Ive been playing around with the framework and like what it does. I have come across an issue that im struggling with.

What i want to does is have a standard url structure, and use the controller if it exists but fallback to use a default controller if not.

for example i would have a general page controller as default which loads in the page content from the database,

so

mysite.com
mysite.com/about
mysite.com/contact

would all use my page controller and index function

but if i had a controller that existed it would use that

mysite.com/forum

would use the forum controller

essentially can you set it somewhere so if the controller does not exist it uses the default controller and index function?

Any help would be appreciated.

Thanks in advance.