Phone register, please help

Is there any way to let my ip phone register to the asterisk sever automatically,but not configure every ip phone’s information in sip.conf in advance? Thank you.

Imagine this:
You put 2 phones on the desk, make phone config - only asterisk IP.
From where You will know how to make a call from first to second phone ?

You have to make some configs.
Anyone have diffrent opinion ?