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[OT] Interesting Windows IP issue

There is one other suggestion I wanted to add to this thread. If it will be 
worth the effort, try running Wireshark on this host. It may help to answer what 
the host is trying to do or even it is trying to grab the proper Internal Lan-10 
address. If you see some strange DHCP handshaking activity, it will help to 
answer what is taking place and assist you if this occurs again in the future.

Best Regards

From: Jerry Feldman <gaf-mNDKBlG2WHs at>
To: discuss-mNDKBlG2WHs at
Sent: Sun, January 23, 2011 7:43:34 AM
Subject: Re: [OT] Interesting Windows IP issue

On 01/23/2011 02:23 AM, David Kramer wrote:
> On 01/22/2011 03:32 PM, Jerry Feldman wrote:
>> On 01/22/2011 03:21 PM, Mark Komarinski wrote:
>>> On 1/22/2011 10:30 AM, Jerry Feldman wrote:
>>>> Yesterday at work, one of my coworkers wanted to make a presentation
>>>> from his company laptop (Windows XP). For some reason his IP address was
>>>> showing 192.168.x.x, not the internal company 10. address. I used my
>>>> Ubuntu netbook to make sure the CAT5E cable was ok, and I certainly got
>>>> a valid 10. address. We moved to another office because the lighting was
>>>> better, and the same thing. We even rebooted his computer. Somehow it
>>>> wanted to remain at 192.168. Our cables are plugged directly into a
>>>> switch that plugs into our firewall. After a while we finally got the
>>>> thing up and running on the corporate network. Note that I had even done
>>>> a IPCONFIG /release and IPCONFIG /renew. I've seen this before on his
>>>> previous laptop. Apparently he does something at home, but when I look
>>>> at properties it shows DHCP.
>>> Use ipconfig /all to verify that a lease is actually getting assigned.  
>>> If it is, you may have a rogue DHCP server on your hands.
>> This has happened before on his previous laptop. I think it has to do
>> with the way he configured it. No one else has the same problem.
> OK, here's a crazy theory.  Windows sometimes tries to "bridge" ethernet
> devices so they look as one device, whether you're using wireless or
> wired.  Maybe it does this via its own nat?
Could be. I didn't have the time to sit down any analyze.

Jerry Feldman <gaf-mNDKBlG2WHs at>
Boston Linux and Unix
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