Command originate SIP/Extension_number@Ip_address

I’m trying to make work my elastix and cisco IP phone and i have the following problem:

With the following comand the phone ring

asterisk -rx “originate SIP/315@XXX.XXX.XXX.XXX application Playback hello-world”

But with the following one, the phone doesn’t ring

asterisk -rx “originate SIP/315 application Playback hello-world”

I mean, if i don’t write the ip_addres, the phone doens’t ring. I have been analyzing it in wireshark, and i detected:

This is the output for the firs command:
5060 315.135647000 SIP/SDP 830 Request: INVITE sip:315@ | 5060 8534

And this one for the second:
5060 39.117858000 SIP/SDP 808 Request: INVITE sip: | 5060 868

The difference between them is after INVITE sip. Does any body how should i configure elastik in order to make it word just with the command:
asterisk -rx “originate SIP/315 application Playback hello-world”

For sure, that is a silly hing, but i can’t get it.

Any suggestion?