Boston Linux & Unix (BLU) Home | Calendar | Mail Lists | List Archives | Desktop SIG | Hardware Hacking SIG
Wiki | Flickr | PicasaWeb | Video | Maps & Directions | Installfests | Keysignings
Linux Cafe | Meeting Notes | Blog | Linux Links | Bling | About BLU

BLU Discuss list archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[OT] Interesting Windows IP issue

I'm pretty sure it was not wireless. We do have a wireless, but it will
pass the DHCP through to the firewall where we will get a 10. address.
All of our office jacks are connected to a Netgear GB Ethernet switch
that is connected to a SonicWall. There should not be a rogue DHCP
server. Again, I tested the connection with my Linux laptop. We also
moved to a different office and I know that connection is good. The
issue is something with his laptop. Additionally his wireless was disable=

On 01/22/2011 03:51 PM, ninurta2005 wrote:
> A rogue DHCP server crossed my mine too. It was odd that under Linux, i=
t grabbed=20
> a IP address from the Lan-10 subnet, but under Windows, it went with a =
> from the subnet; I am guessing using the same Ethernet =
cable. As=20
> a rule, you can't have DHCP addresses issued from two different private=
> range subnets on the same ethernet cable via the same subnet. Since Cat=
5E was=20
> mentioned, I suspected that it wasn't getting a wireless IP. Laptops wi=
ll have=20
> two ethernet connections, one for wireless and one for cabled Ethernet.=
> Disable the wireless radio to be sure, it is only way to assure the hos=
t is=20
> receiving a wired DHCP request response.
> If you have a testbed that is also using the Lan-10 Private range, atta=
ch the=20
> laptop to that network and see if the  problem follows the laptop. I cr=
eated one=20
> using Openwall with DHCP enabled. Ditto for IPCOP and Smoothwall which =
> just as well.
> Best of luck,
> Paul
> ________________________________
> From: Mark Komarinski <mkomarinski-GqRSzq0LZOzYtjvyW6yDsg at>
> To: discuss-mNDKBlG2WHs at
> Sent: Sat, January 22, 2011 3:21:01 PM
> Subject: Re: [OT] Interesting Windows IP issue
> 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 w=
>> 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 go=
>> a valid 10. address. We moved to another office because the lighting w=
>> 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 do=
>> 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.

Jerry Feldman <gaf-mNDKBlG2WHs at>
Boston Linux and Unix
PGP key id: 537C5846
PGP Key fingerprint: 3D1B 8377 A3C0 A5F2 ECBB  CA3B 4607 4319 537C 5846

Discuss mailing list
Discuss-mNDKBlG2WHs at

BLU is a member of BostonUserGroups
BLU is a member of BostonUserGroups
We also thank MIT for the use of their facilities.

Valid HTML 4.01! Valid CSS!

Boston Linux & Unix /