I do not know much about Macs. Someone that know Macs on here might be able to give a better answer, but this page references a way to find that ip address on a Mac by installing nmap & using that to find the ip address, http://www.raspberrypi.org/documenta.../ip-address.md I used a google search for "how to find the ip address of a raspberry pi on a mac" to find this page.