...
<authentication mode="Forms">
      <forms cookieless="UseCookies" enableCrossAppRedirects="false" loginUrl="~/Account/Login" name=".ASPXAUTH" path="/" requireSSL="false" protection="All" slidingExpiration="true" timeout="2880" />
</authentication>
...

    
...            
string cookiePath = FormsAuthentication.FormsCookiePath;
FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(version, login, issueDate, expiration, isPersistent, userData, cookiePath);
string encryptedTicket = FormsAuthentication.Encrypt(ticket);
HttpCookie auth = new HttpCookie(".ASPXAUTH", encryptedTicket) { Expires = DateTime.Now.AddYears(3) }; 
...