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I have created a web application hosted in IIS 7.

When I deploy my web app to customers it can be reached via the computer name most of the time, however sometimes it will suddenly stop working. The site cannot be found. At that point you can use the IP address to access the site bu then the symptoms switch around once more. The IP address fails but you can access it by the computer name. The process will repeat over and over ad infinitum

Can anyone explain the alternating, exclusive-or accessibility I am witnessing? I imagine it is a DNS issue.

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First step: do you have an internal DNS server on your network, and are the computers in your network mapped to it? If so, how? Dynamic Updates, or can you create an A entry in there for your server? If not, then it may be that your network is using NetBIOS name resolution. – Mark Henderson Feb 13 '12 at 19:37
That's not enough information to diagnose the problem (unless all your customers have flaky DNS)... You should look at App and System event logs, take a memory dump of a w3wp related to your app and investigate it, and potentially actually do some dev-related troubleshooting, especially if it's customers and not just a customer. What you're describing sounds like an app bug to do with state management. Does it break for all users at once, or just some users, or each user individually? Much, much, much more information needed to diagnose anything. – TristanK Feb 13 '12 at 21:41
each customer is separate, on their own network, but I do imagine they set up their networks the same, so it is possible that they do have flaky DNS. If it is an issue on my side alone, I would think I would see the same issues when I test locally, however, I only see this on their networks. I will look into the logs and try a dump of w3wp. Thank you, I am really just looking for something to go on here since I know next to nothing of networking; am software developer – RichardJohnn Feb 14 '12 at 18:19

If you're doing this on your machine, then you are likely using DHCP and your IP is possibly changing. Also check your IIS bindings.

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IP addresses are supposed to be staticd on my customer's network. My IIS bindings the default, simply http, all unassigned ip addresses on port 80, no host name – RichardJohnn Feb 14 '12 at 18:18
Do you get the same results for ping? Is there a network engineer you can ask to watch your packets from a user's machine? This may be a network issue and not a host issue. If I controlled the server and not the clients I would get access to a different box on that network so I could do my own testing and not rely on user reports. – Bret Fisher Feb 14 '12 at 22:47

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