Port Forwading Question

Ok I have 10,000-20,000 forwarded to the pbx? what about port 5060? do I need that forwarded as well? I remember being told that for each extension the port should change. For EX:
EXT:100 5060
EXT:101 5061
EXT:102 5062

My question is number one is this correct? Also, I should forward 5060,5061,5062 and so on to the IP phones not the pbx server?

Thank You,