iPrint Appliance What tcp/udp-port do Avahi use?

Hi!
I'm trying to set up AirPrint. I have one printer activated for AirPrint, but my iPad can't see it.
I guess the problem is Avahi is broadcast AirPrint over some sort of protocol.

My iPrint-server is connected to another VLAN and only iPrint and HTTPS is opened trough access-list.
So i need to know what protocol(port/udp/tcp) Avahi announce AirPrint-printers.

RS