AirPrint requires Bonjour, and Bonjour is based on multicasts.
If the router correctly supports multicasts over the wireless network
(and bridges them to the wired Ethernet LAN, if the target device is
there), it should work with AirPrint in that context.
Apple's routers certainly support multicasts (including bridging to
Ethernet), as Apple uses Bonjour extensively for protocols like
AirPrint, AirTunes, AirPlay and iTunes home sharing.
I have AirPort Extreme and AirPort Express routers, and they certainly
work with AirPlay, AirTunes and iTunes home sharing. I haven't used a
printer with built-in AirPrint support so I can't be certain that it
would work, but I would be very surprised if it didn't.
--
David Empson
dem...@actrix.gen.nz