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I am reconstructing (with a different machine) a network situation with a Windows Server 2008 R2 machine with IIS. For some years, I have run this using a Comcast Business connection. The previous server failed, and I'm replacing it. The router firmware (the way Comcast handles the connection to the Internet) seems to be correct (I specify the IP address of the server in the place for Port Forwarding--TCP, port 80).

But attempting to access the site via my publicly available site name (or its IP) yields "cannot display page." From within my home network, entering http://[that server's IP] gives the desired IIS result.

Can anyone suggest what might be going wrong here?

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Is your home network the same network we're talking about here ? – TristanK Jul 29 '11 at 2:18

Usually, "home-style routers" have 2 places where you should do the change. Firewall & Port Forwarding. You might want to check if there's something similar on your router.

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Sounds like a NAT issue to me. – DKNUCKLES Jul 27 '11 at 16:44
Only Port Forwarding offers any relevant configuration options. The Firewall tab just offers a couple checkboxes. – Michael Broschat Jul 28 '11 at 10:30


  • Internet DNS should point the site name at the external, public IP address of the NAT/router/firewall/thing. I assume you have only one public IP address.

  • Internal DNS or HOSTS files for internal network clients should point the site name at the internal, private IP address (192.168.0.x, I'd guess)

  • Your router/firewall must forward all TCP port 80 traffic from the public network to that IP address on the private network.

    • You can't do this for multiple computers, so if there's a rule for the old server that does this port forwarding, or HTTP Server forwarding, or DMZ creation, that will have to be removed before any of this will work externally.
    • alternatively, you could use the same IP address the old machine used; it's unclear why you didn't do that.
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Sorry for the delay. Comcast decided to replace the router, and that just happened yesterday.<br> – Michael Broschat Aug 6 '11 at 13:04

I would suggest first narrowing down your problem set. Accessing a server via its direct ip or localhost is not always the same as acessing it via a hostname. Things to try:

1) Nslookup your external hostname. Is it pointing at the right IP?

2) Make a mapping in your hosts file that maps the intended hostname to the local server IP. Does the site work now? This is best attempted from another machine on the same network.

This will give you an idea of where your problem might lie instead of just assuming its a router issue.

if trial 1 is incorrect then you need to check with your dns provider and confirm all the settings are correct.

If trial 2 doesn't work then you have something wrong with the configuration of your binding or firewall setting on the server.

If if trial 1 and 2 both work its most likely some forwarding issue with the router. You can start checking if any traffic is forwarding through the router.

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Why is accessing the computer via it's direct IP address any different than accessing it via a hostname? A hostname is simply a DNS A record associated with the IP address, so why would you need to troubleshoot DNS when he doesn't even have a direct IP address connection? – DKNUCKLES Jul 27 '11 at 16:43
1. NSLookup confirms the correct IP, etc. 2. We made the entry in HOSTS. Now, you can see the IIS page but only from a machine not in the subnet. Any machine on my network just gets a 404 error. – Michael Broschat Jul 28 '11 at 10:32
See below (6 Aug 2011) – Michael Broschat Aug 6 '11 at 13:03
up vote 0 down vote accepted

The situation has clarified a bit, so I'm entering this "new" section. The world sees my site(s) as it should be. I cannot see what machines outside my home network see. I presume that this is because I have not yet run the ROUTE command. [However, entering the local IP shows what the public sees via the public IP] I see two interfaces, corresponding to the two NICs on my system. Both are on the same subnet: 10.1.10.n Should I continue to use two NICs (I do so to provide separate paths for WAN and LAN)? I know how to direct all LAN traffic through one NIC, but with both of them on the same subnet, can this work? My public IP is almost certainly handled completely by my Comcast arrangement. In other words, I never actually see that address, right? It seems to me that if my public IP were, then all traffic to that address would end up at my router but that the address would then have no meaning to my home network (which knows only the 10.1.10.n stuff). Is this correct?

Last update, 11 August 2011 Although there are still many questions concerning this event, the bottom line is that Comcast replaced the router (that provides their Internet signal to me) and all works as it did before. Here is how easy it should be: 1. Comcast supplies the router/modem from which I take my signal. 2. I configure that router to pass all Port 80 traffic to my web server. Additionally, I must tell "the world" (Network Solutions, in my case) what my IP is. That is provided to me by Comcast.

The situation I started with was much more complex (involving virtual servers, etc), but I had to get it down to the basics in order to get the problem solved.

Thanks for the many suggestions and insights into networking.

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