Question : How To Share An Extension Between An IP Phone and Softphone?

I am looking for a way to share an extension between my IP phone and a softphone.

I don't want to get into a situation where they are fighting for the registration of the phone number, I would like it so that if I am out with my laptop my softphone can be connected with out it disconnecting my IP phone.  So ideally the call could be answered on either the soft phone or the IP phone.

I know this can be done in Asterisk with a Call Queue, or ringing 2 different extensions at once, but what I want is 1 phone number that can be answered on both phones with out disconnecting each other and fighting for the registration.  So essentially I want to share the "line" as it were.

Is this possible to do?

Answer : How To Share An Extension Between An IP Phone and Softphone?

Normally, the SIP device ID and the extension number would be the same. Furthermore, the IP phone may even reject the INVITE from Asterisk if the username and extension number don't match. However, because the entities are independent within Asterisk it means you can do tricks like this:

SIP.CONF:
[2300desk]
type=friend
username=2300desk
secret=pass1
etc
[2300soft]
type=friend
username=2300soft
secret=pass2
etc

EXTENSION.CONF:
[mycontext]
exten => _2XXX,1,Dial(SIP/${EXTEN}desk&SIP/${EXTEN}soft|30)