pix501, port redirecting, aliases

No, you have to do it like this:

---publicIP---pix501---LAN(192.168.1.x)---Router---VoIP(10.10.10.111)

You don't need a real router - a cheap routing switch will do.

access-list out_to_in permit udp any(1) interface outside eq 16384 route inside 10.10.10.0 255.255.255.0 192.168.1.Y(2) static (inside,outside) udp interface 16384 10.10.10.111 16384 netmask

(1) = Do not use 'any' if you know the needed IPs (2) = The IP address of the new router

Thank You