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Cannot access the website from the Internet

(Kristofer Gafvert, September 23, 2007)


Each week I take two questions from the IIS newsgroups (or IIS forums) that I think is of public interest, and I answer them here as well. Questions and answers may be modified to be more general and more useful for everyone.

Cannot access the website from the Internet

I cannot access the website from outside our local network. I can access it from the server itself, and I can also access it from another machine on the LAN. But when I try to access it from the Internet, it always returns with "Internet Explorer cannot display the webpage".

Since it works internally, we know one thing, IIS is working fine. So the problem seems to be related to networking.

The most common reason for this to happen is that port 80 is blocked. It can be blocked by your ISP (common today), in your hardware firewall/router (if you have any) or in Windows itself (Windows Server 2003 has a built-in firewall). To allow traffic on port 80 thru the Windows Server 2003 firewall, open the Windows Firewall application from Control Panel, click on the Exception tab and add port 80 to the list of allowed services.

Other common reasons for IIS to be working internally but not externally are:

  • Name resolution (if you use a domain name) is not working outside the LAN. Either you use the wrong name (for example the machine name, which does not work on the Internet) or the DNS name does not resolve to the correct IP address (or does not resolve at all)
  • NAT/Router forwards the request to the wrong IP address.
  • IIS binds to an IP address that is used internally, but not externally.

Applies to [?]

IIS 6.0