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I've been in charge to move a web servers from our office to a datacenter. Its IP has changed, and I have updated the DNS accordingly. This was 6 days ago.

Lets say its DNS name is customerarea.mycompany.com, its old IP was 83.xxx.xxx.205 and its new IP in the datacenter is 37.xxx.xxx.8.

Everything seems to work fine for everybody, except for one of my colleagues: from its computer (Windows 7), a ping or a nslookup will resolve customerarea.mycompany.com to 37.xxx.xxx.8 (the new IP). But when using any browser (firefox, chrome or IE) he is still redirected to the old ip (83.xxx.xxx.205).

I have checked the DNS propagation (https://www.whatsmydns.net) and everything seems ok. I have tried to configure a proxy, to reboot the machine and to change the DNS to 8.8.8.8 (google's DNS) but with no luck.

When looking at chrome's dns cache, the IP is still 83.xxx.xxx.205.

This is driving me mad! What am I missing?

EDIT: As a workaround, I have installed a reverse proxy on the old IP, and it points to the new IP. Not for a single computer, but just in case some of our customers encounter the same problem.

However I don't like to leave a problem without understanding what's going on, so if someone have an idea...

Olivier Leneveu
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  • Have you tried clearing the browser cache? Have you looked at the HTTP exchange just to see that it's going where you expect? – user May 26 '16 at 13:27
  • Yes I have cleared the cache, and checked the exchanges with fiddler and firebug. There is no doubt that it is still pointing to the old IP as another webserver with a different content is now hosted on this IP. – Olivier Leneveu May 26 '16 at 14:21
  • Are the browsers setup to use a proxy? – Ƭᴇcʜιᴇ007 May 26 '16 at 14:30
  • Anything in the hosts file? – DavidPostill May 26 '16 at 15:17
  • Did you flush DNS resolver cache : `ipconfig /flushdns`? – DavidPostill May 26 '16 at 15:18
  • The browsers were not configured to use a proxy. I have configured one to see if it would change something but it wouldn't. There is nothing in the host file relating to that IP. – Olivier Leneveu May 26 '16 at 16:33
  • I've just tried a `flushdns`, but it doesn't change anything. Anyway, a `ping` resolves the right IP (the new one). – Olivier Leneveu May 26 '16 at 16:39
  • A DNS could be "static" in the adapter TCP/Protocol settings, do a properties on the adapter(s) and check EVERY protocol for manually static addressing and alternate dns etc. What is the possibility that IP4 stuff is working but when it is using IP6 ? I donno for IE much data is stored in the index.dat for previous resolves, not for dns. chrome and firefox can have thier own dns caches. if flush does not work disable (temporarily) the "dnsclient" service. If there is some temp stuff that your not finding Ccleaner might find it. An AV or malware protect program that thinks it is helping ? – Psycogeek May 26 '16 at 17:42
  • DNS for all protocols are set via DHCP. Anyway, the server does not have an IPv6 address. I've cleared the chrome's DNS cache (http://superuser.com/questions/203674/how-to-clear-flush-the-dns-cache-in-google-chrome) and stopped the DNS client service with no luck. We all have the same AV on all of our computers, and only one is experiencing this behavior. – Olivier Leneveu May 27 '16 at 08:08
  • More stupid stuff , LMhosts is not default on even in win7 (sample) but i read something about it being used like hosts for local speedup pointing to local lan computers. It is assumed you looked in hosts, but there is that too if some sysadmin set that. It wouldn't take too long to run a registry search for the a specific IP number/range. Searching all the file contents in the system for a number that gets pointed to, thanks to windows search settings and indexing (what gets searched) would not be great, but if you have some 3rd party search that looks inside files (file content). – Psycogeek May 27 '16 at 09:45
  • Give this a try. use the host file. Read about how to save to the host file [here](http://www.howtogeek.com/howto/27350/beginner-geek-how-to-edit-your-hosts-file/) add this as a line. `# 37.xxx.xxx.8 customerarea.mycompany.com` oh his PC – NetworkKingPin May 27 '16 at 10:02
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    If you want to look up an IP address, use `nslookup` – Oliver Salzburg May 27 '16 at 11:06
  • Forcing the IP using the host file does not change anything. As said in my post `nslookup` resolves the right IP. – Olivier Leneveu May 27 '16 at 14:00
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    @Oliver Salzburg: I'm not sure about this point, but I believe that `nslookup` might return a different IP than a `ping` as `ping` might get it's result from the cache while `nslookup`will always query the DNS. So `ping` should be closer to what append to a software when it resolves an IP. – Olivier Leneveu May 27 '16 at 14:30

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Did you try to look into the 'hosts' file? It's the first thing I'll do in the same circumstances. You can find it in the 'C:\Windows\System32\drivers\etc' folder

ipconfig /flushdns

also can help, but reboot will also do the same, so I thing there is either hosts file or he can use another DNS server with old data in it.

You can also look here for similar troubleshooting examples.

Valentin
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  • These points have already been studied in the question or in the comments. The main problem is that on the same computer the same DNS name resolves to a particular IP when using a browser and to a different one when using any other software. – Olivier Leneveu May 27 '16 at 14:36
  • Do you using a SOCKS proxy with remote DNS feature, maybe? – Valentin May 29 '16 at 05:08