Friday, 17 September 2004

Windows XP SP2 Network Problems

Chizuko's laptop finally picked up XP SP2 off the Windows Update site on Wednesday night. I'd updated mine about a month ago, using the manual download, but after the minor problems I'd had with it (mostly due to it not detecting Kerio Firewall, and installing its own) I decided to leave hers for the Windows Update version.

After the update (again, I had to manually disable Windows Firewall because it did not detect Kerio), her PC was unable to load any web sites. Actually, that's not quite true. It loaded Google, so I knew her wireless card was working, but nothing else. I started trying to search for problems on Google, and using the Google cache to read them, but eventually I wanted to follow further links, so I grabbed my laptop and worked with one on each knee. None of my searches turned up anything relevant so I decided to document my findings here.

Because I could reach Google, I knew that the basic hardware and driver level of the network was working. I also figured out that DNS resolution was working for all sites. Knowing a bit about networking (what is the average user to do in this situation?) I suspected MTU problems. After searching for the method of changing the MTU, I set hers to 1452 (a number I pulled out of a hat, actually it was the lowest of several values I saw being recommended for people having DSL problems). After a reboot, everything was working happily again.

So what is different between my laptop, which worked, and hers that didn't?

  • Mine: XP Pro, Hers: XP Home

  • Mine: TI ACX100 based wifi card, Hers: Prism GT based Dlink DWL-G650 wifi card

Other things that might be relevant:

  • Access point is a Linux box with an Atheros based Dlink PCI card running the madwifi
    drivers in master mode.

  • Access to the internet is via a DSL modem connected to the Linux box, using PPPoA, and
    an MTU of 1500 (default).

  • Laptops are using a private address space ( and the Linux box is NATing them to a static IP.

I don't know which of those is the key to the problem, but I'd say the wireless card is most likely. All I do know is that mine works with the default MTU (1500), as did hers before SP2 was installed. I guess I could try swapping the wireless cards, but I'll have to dig up the driver disks.


Anonymous said...

Thanks for posting this bit of experience. Until
SP2, I was taking in the steady dribble of MS patches with automatic update service to my XP boxes. They live behind a zonealarm pro firewall
in a dedicated 2-NIC firewall machine, an ancient pentium running Win2000 and providing NAT, all ethernet connections to a hub on the LAN side of the firewall so I am
not quite so much at the mercy of the marauders
on the information sewer highway.
When I heard of the trouble folks have with SP2, I
set it to just let me know it had the latest patch
but not install. The more experiences such as yours
that I read of, the happier I am to hold off installing. There are too many "thumbs up/thumbs
down" advisories on SP2 and not enough details
about what breaks or fails.

BTW, I am museumpeace on slashdot and I expect you were jesting but no, I don't work for SCO and do think
they are vile. My comment about the Unix ancestry of Linux was, shall we say, more poetic than technical. If I had to expand on that every time by saying "Unix begat the posix standard and linux was coded to the posix standard" I would be even
more of a bore than I already am!

Tidy blog, makes me imagine I could run one of my own.


Anonymous said...

I've now had similar problems with two Dell laptops (a work one and one I bought Chizu after the power socket separated from the motherboard on the old Toshiba this post was about. These times though, the MTU registry hack did not fix it. The problem turned out to be power save options in the wireless card for Chizu's new laptop (the transmit power was being reduced to the point where it was marginal), and "burst mode" being enabled on the work laptop. Trust Dell to ship with problematic settings enabled.>