I can't figure out how to search just this thread...
Sorry if this somewhere in the 50+ pages.

I have an Apple Airport Extreme router.
The subnet is fixed at 255.255.255.0 and
cannot be changed.

The instructions on page one state:
Make sure your router's subnet is 1, ie 192.168.1.x

Will 255.255.255.0 work?

Thanks   ...   Ken