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 (10.0.0.0/8) 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.