IIS randomly returning INET_E_RESOURCE_NOT_FOUND

bootstraphttp-status-code-404iis-7ip

I am using IIS 7 on Windows 2008 Server for an ASP.NET 4 application using Bootstrap. The server has a private IP address to use at work, but is also accessible through a public IP address from outside. Our Internet access provider does the forwarding for us. The server is also running the F-Secure antivirus system.

When I browse the web site from the server itself, using either the private IP or the public one, it works fine. But when I use a remote client (using the public IP, obviously), it works randomly. A typical scenario goes like this:

  1. I type the web site URL on my browser. I get home page.
  2. I click on a link to navigate to another page. I get an INET_E_RESOURCE_NOT_FOUND error.
  3. I hit refresh on the browser. I get the page.
  4. I click on another link. I get the page.
  5. I click on another link. I get an INET_E_RESOURCE_NOT_FOUND error.

And so on and so forth. It is apparently random. Sometimes the server returns the page, sometimes I get the INET_E_RESOURCE_NOT_FOUND error. It happens from every client I have tried, from Edge on a Windows 10 machine to Safari on an iPhone.

Some other times, the server fails to deliver the home page when I first browse to it from a client computer. I retry a few times to no avail. And then, after perhaps 5 or 10 refreshes, I get the page. And from that point on, it works OK until, eventually, it fails again.

As far as I understand, INET_E_RESOURCE_NOT_FOUND does not mean that a page was not found (that would be a 404), but that the server could not be found. It is usually associated with a DNS or proxy error.

I have been looking at IIS log files. As far as I can see, sometimes logging gets interrupted with entries such as this one:

GET /fonts/glyphicons-halflings-regular.woff - 80 - 193.144.38.100 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/52.0.2743.116+Safari/537.36+Edge/15.15063 404 3 50 78

Apparently, the client is trying to get a fonts file and the server returns a 404 error. The font file is on the server in the right folder, so I am not sure why it's failing to find it.

EDIT. I have now fixed the issue with the font file (which was due to a missing MIME type entry on IIS), but the random INET_E_RESOURCE_NOT_FOUND errors remain. The 404 with the font file is likely to be a red herring.

EDIT. I have another issue with this same web site, which may be related. Please see here: https://stackoverflow.com/questions/43814006/smtpexception-in-asp-net-application-with-remote-browser

Any ideas? Thanks.

Best Answer

You said that the ISP is doing the forwarding for you, which suggests that they are proxying/port-forwarding to an internal IP and that your server only has one IP address (likely a private one).

If this is true, then it sounds like their proxy server is having issues connecting to your IIS server (for any number of reasons) and is the one returning the error. I would ask the provider to check the logs on their router/firewall to see whether this is the case.

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