Thursday, November 01, 2007

Tech: Leopard Airport issues

A lot of people are having issues using Airport after upgrading / installing Leopard. I ran into the same issue as well. My problem was resolved by manually setting the Airport MTU to 1492.

For some reason my ISP's implementation of PPPoE requires me to manually set the MTU on all the systems in my network. I had a script that did this automatically every time I switched to my "Home" location. This of course broke after the upgrade. I decided to try my luck and see if the proper MTU's would be automatically detected and set, so I didn't bother to set it manually.

It turns out that without the right MTU set, I could not join the Airport network at all. "Connection failed" would be reported in the Airport preferences, and the following appeared in the system log:

Nov 1 22:02:45 Macintosh airportd[225]: Error: Apple80211Associate() failed -3Nov 1 22:02:45 Macintosh Apple80211Agent[195]: Error: airportd MIG failed = -3 ((null)) (port
= 27139)Nov 1 22:02:45 Macintosh Apple80211Agent[195]: Error joining XXXXX: Connection failed (-3 resul
t unavailable)

Setting the MTU manually fixed this issue immediately.