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From: Jeff Liebermann on 27 Jan 2008 12:29
Jennifer R <james.raden(a)gmail.com> hath wroth:

>This is ridiculous.

What is rediculous? The problem or the question?

>My Dell Wireless 1490 Dual Band WLAN Mini-Card on
>a Dell Precision M90 Win XP SP2 just refuses to grab its DCHP address
>half the time from public access points.

Let me guess. This only happens when you've successfully used your
laptop at your home or office, and then go to a coffee shop?

>Everyone around me is humming
>away with no problem. I've got it configured as DHCP, everything
>default, but it doesn't work. During a "repair" or a "ipconfig /renew"
>I can see that it does indeed receive a couple of packets, but it's
>doing nothing.

This is sounding familiar. You're close.

>If I run Ethereal/Wireshark I see that the DHCP server is sending two
>DHCP OFFER packets to my machine, but my machine just ignores them.
>This seems to happen in half the public access points I go to (over
>which I have no control), and it's inconsistent. Some days it works,
>some days it does not.
>
>Do I really have to run Wireshark and dissect the DHCP OFFER packets
>to manually configure my Wireless Ethernet card every time? Is there
>some mysterious configuration parameter that will help solve this?
>
>Thanks.
>
>- Disgusted with Dell

Right. Let's blame Dell. The first step to solving a problem is to
blame someone. Dell will suffice for now.

I'll assume that the coffee shop is not running out of DHCP addresses.
I created this problem at some of my coffee shop hot spots using
DD-WRT by specifying that DHCP save the leases in NVRAM. That worked
until I filled up all the slots, where it decided that it didn't want
to add any more clients.

You were close. Try this next time:
Start -> Run -> cmd <enter>
ipconfig /release
(wait a few seconds)
ipconfig /renew
ipconfig (to display the results)

What is happening is that Windoze XP SP2 thinks you're still at home
or work and is trying to renew the previously assigned IP address
forever. This is especially true if the IP address of the access
point is the same at work, home, and at the coffee shop, a common
problem. The DHCP requests are done with MAC broadcasts, but the
renewals are done using IP addresses.

This was fixed in some obscure wireless networking update from
Microsoft. It was also an issue with some wireless clients and
drivers. Check if you have the latest drivers and wireless updates.

You might also wanna try a DHCP tester at:
<http://www.weirdsolutions.com/weirdSolutions/files/products/desktopSoftware/desktopQueryTool/querytool_free.exe>
There's a bit of a trick to using it. Type in literally anything into
the "Device Identifier" field. Check the "Request response" box.
Don't check the "Use BOOTP" box. You do NOT need to be connected for
this to work. Mine returns:
option PKT:Opcode=2
option PKT:HType=1
option PKT:HLen=1
option PKT:Hops=0
option DHCP message type=5
option PKT:Flags=32768
option PKT:Seconds=0
option PKT:XID=41
option PKT:SName=
option PKT:Boot file=
option PKT:CIAddr=0.0.0.0
option PKT:YIAddr=192.168.1.100
option PKT:SIAddr=192.168.1.1
option PKT:GIAddr=0.0.0.0
option PKT:Magic cookie=99.130.83.99
option Subnet mask=255.255.255.0
option Gateways=192.168.1.1
option Domain name servers=192.168.1.1
option Broadcast address=192.168.1.255
option Server identifier=192.168.1.1
option DHCP address lease time=7200
option DHCP renewal time=3600
option DHCP rebinding time=6300
option PKT:CHAddr=00
which is rather interesting as the machine I'm running it on has a
static IP address. Also, the results are rather "interesting" if the
coffee shop has more than one DHCP server running.


--
Jeff Liebermann jeffl(a)cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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