Why really short timeout in ASP.NET MVC?

I have an MVC 2 application where the timeout is set to 2880 (minutes as I understand it, but even if it is seconds there's a problem):

<authentication mode="Forms">
  <forms loginUrl="~/Account/LogOn" timeout开发者_Python百科="2880" />
</authentication>

Now this should then mean 48 hours, or at least 48 minutes (if the value is seconds). But the user is logged out after as little as a couple of minutes of inactivity...

Why is that? Any help appreciated!

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Found the answer finally after a lot of Googling...

You have to set a custom machinekey in the web.config file. I used this generator:

http://aspnetresources.com/tools/machineKey

This seems to have to do something with "recycling" on the web host, which causes the user to be logged off, if I understood it correctly.

Anyway, it works fine now!

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2880 is given in minutes. It will logout automatically if you add slidingExpiration="true". See example below.

 <forms loginUrl="~/Account/LogOn" timeout="2880" slidingExpiration="true"/>