I have to implement a function in an Asterisk (any version would be ok for me), that allows me to register my extension in any phone I want, just dialing a feature code or something similar.
For example, I work at the IT department and my extension is 1000. For some reason I have to go to another part of the company where there is a phone and I want to use my own extension 1000 there, instead of the extension that is already registered there (1001 for example).
I know that some PBX are able to do that, if properly configured, like Siemens for example, where I can go to any phone I want, type a code followed by my extension number and I can make and receive calls like if I were at my desk.
Separate your extension from your SIP endpoint/peer. On dialing some (feature) code from SIP endpoint, enter your extension (and store this details in astdb so that when someone dials the extension, you dial the latest SIP endpoint)