Windows 2008/ IIS7.5 / Classic ASP/ ASP.Net intermittent 403 errors

We’ve just set up a new dedicated server at some hosting provider, running Windows 2008 Server R2 and IIS7.5.

Sometimes the site works, sometimes, part of the site runs and I can see a 403 error in Firebug. At other times, I only get an IIS error page saying:

“403 – Forbidden: Access is denied. You do not have permission to view this directory or page using the credentials that you supplied.”

This information was not enough to troubleshoot this problem so I checked IIS log files for HTTP STATUS CODE 403.  I found some lines like this:

#Fields: date time s-ip cs-method cs-uri-stem cs-uri-query s-port cs-username c-ip cs(User-Agent) sc-status sc-substatus sc-win32-status time-taken

2011-04-26 14:03:41 xx.xx.xx.xx GET /Calificaciones/Calificaciones.aspx – 80 – yy.yy.yy.yy Mozilla/4.0+(compatible;+MSIE+7.0;+Windows+NT+5.2;+WOW64;+.NET+CLR+2.0.50727;+.NET+CLR+3.0.04506.30;+.NET+CLR+3.0.04506.648;+.NET+CLR+3.0.4506.2152;+.NET+CLR+3.5.30729) 403 502 0 249

So I got HTTP STATUS CODE 403, SUB STATUS CODE 502. Searching for this on Google I found this page:

Server – Windows 2K8/IIS7/ColdFusion throwing intermittent 403 errors

This gave me some light on the problem and I began to search for IP filtering on IIS configuration settings.

1. Open ISS Manager.

2. Go to your website.

3. Go to  Features/IIS/Dynamic IP Restrictions.

Source: IIS.Net: The Official Microsoft IIS Site

4. Set the appropiate values or disable restrictions. In my case, I doubled former values and it’s working like a charm rigth now.


Dynamic IP Restrictions



2 responses to this post.

  1. I hardly comment, however I looked at a few of the remarks here Windows 2008/ IIS7.
    5 / Classic ASP/ ASP.Net intermittent 403 errors | Nathan.

    I do have 2 questions for you if it’s allright. Is it just me or does it look like a few of the comments come across like they are coming from brain dead folks? 😛 And, if you are writing at other online social sites, I’d like to keep up with
    anything fresh you have to post. Would you list of the complete urls
    of all your public sites like your twitter feed, Facebook page
    or linkedin profile?


  2. Hey there! I just wanted to ask if you ever have any issues with hackers?
    My last blog (wordpress) was hacked and I ended up losing
    many months of hard work due to no backup.

    Do you have any methods to stop hackers?



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