Asp.net persistent login cookie expires randomly

Question

I'm trying to implement a login form with the remember me functionality in ASP.NET 4.0.

I've set the timeout option in the web.config to 1 year (525600), but after a random amount of time after I logon, I always get logged off.

The cookie is created correctly, I can see it in the browser with the right expire value (september 2014), but it seems that this cookie after some time is not readed by the ASP.NET environment anymore.

I tryed to login with:

FormsAuthentication.RedirectFromLoginPage(username, true);

or:

FormsAuthentication.SetAuthCookie(username, true);
Response.Redirect("/");

or with this custom code:

DateTime expiryDate = DateTime.Now.AddMinutes(FormsAuthentication.Timeout.TotalMinutes); 
FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(2, userid, DateTime.Now, expiryDate, true, String.Empty);
string encryptedTicket = FormsAuthentication.Encrypt(ticket);
HttpCookie authenticationCookie = new HttpCookie(FormsAuthentication.FormsCookieName, encryptedTicket);
authenticationCookie.Expires = ticket.Expiration;
Response.Cookies.Remove(FormsAuthentication.FormsCookieName);
Response.Cookies.Add(authenticationCookie);
Response.Redirect(FormsAuthentication.GetRedirectUrl(username, false));

But the result is always the same. The cookie is present, but after some time it's not used anymore.

The Web.config is like so:

<authentication mode="Forms">
    <forms loginUrl="/login" defaultUrl="/" name="appName" path="/" timeout="525600" slidingExpiration="true"/>
</authentication>

The odd thing is that in my local test environment (ASP.NET Development server) things works correctly. Only in the production environment it is not working!

Answer 1

@Felipe Garcia: I don't know if I'm using a load balancer, I'm on a public server. But I tryed to config the MachineKey as you said (using the generator here ) and now it seems to work correctly!

Thank you!