I have one end user on Windows XP Pro with IE 6.x who, for unknown reasons, will be able to access our internal Web site/databases and then he will suddenly get kicked out (no one else accessing the same site is experiencing this problem). And he can't access any internal sites, although he can access external Web sites like Google, Microsoft, etc., without any problems. His TCP/IP setting has an assigned static IP address and specific DNS entries, both internal and external, listed in order of precedence, which have not changed. I can stop and start his DNS client service and get him back on for a week or two -- but then it happens again. I don't know why this is occurring or how to prevent it from happening. Any thoughts?
Hmm... I can't fix the problem, but I can reassure you that it doesn't make sense. If nothing else, IE caches the DNS results. IE only performs a DNS query when the site is initially contacted. If the Web site doesn't link to a URL with a different host name, the browser will continue communicating with the Web site until it's closed, even if the DNS servers are offline.
The fact that he can't access any internal sites is interesting. There could be a number of issues besides DNS, though. Have you checked to see if he can access the site by using the IP address? Next time this happens, enter the IP address of the site into the browser (for example, http://192.168.1.10). If that works, then DNS is probably your problem. If it doesn't work, it's probably a connectivity issue.
If DNS does end up being the problem, use the NSLOOKUP tool to further isolate the issue. NSLOOKUP allows you to manually query a specific DNS server. Issue the command like this:
For example, if the hostname you're troubleshooting is internal.pri.org, and your DNS server is 192.168.10.10, you would issue this command:
NSLOOKUP internal.pri.org 192.168.10.10
If that fails, then you've definitely got a DNS problem. Execute the exact same command from another system to eliminate the possibility that it's a server-side problem. If it's not a server-side problem, you're going to need to replace a file. I would start by re-installing the latest service pack (and then, of course, re-installing all patches).
If the NSLOOKUP query succeeds, then the problem is either with the client's DNS configuration or with Internet Explorer. Double-check that the DNS servers are configured identically to other clients (including the order of the servers). If so, try re-installing IE.
Hope that helps. Good luck.
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