[Freeswitch-users] Freeswitch port numbers assigned to phones

Hi All I am looking for some insight into FS port numbers. The default internal port number is 5060 and when the IP phones register with FS, one of the phones gets assigned 5060 and the remaining phones get a random port number assigned (I am using this command to see the port numbers: "sofia status profile internal reg"). How is this random port number decided on? How can I tie a phone to a specific port number? Thanks Dion.