I have been using an Apple Airport Extreme (Generation 5) for about a year. Gotta say, it is one of the most stable WIFI routers I have ever used.

I recently noticed there was a firmware upgrade when logging into the admin interface. Great lets update!

A day or two later I can’t use FTP. What’s going on, is my ISP blocking FTP? That would be crazy, as FTP is still (despite security issues) the primary method to publish websites. I suspected it could be the router, but I don’t have any outbound rules or limits in place…

A couple of Google searches and sure enough. The latest firmware in AirPort Extreme and AirPort Time Capsule have broken FTP implementations.

All is not lost. You can easily downgrade back to firmware 7.6.1 to get your FTP functioning again. If you are running Gen. 6 of the AirPort Extreme you can’t roll your firmware back that far, consider returning it to Apple