Register with upstream AFTER register from client?

Hi!

Is it possible that asterisk may register with a SIP provider, after a client
registers with asterisk (instead of doing it during startup).

I would need this, because calls should only be routed to the asterisk if
the client is connected with his sip phone. If asterisk registers from startup
as normal it would black hole calls for this extension.

bye an thanks
AlexTe

Out of the box no. I believe there is way to register using real time (though I have never tried). You can query asterisk every so often to see if the user is registered. If they are then change the field in mysql to register with the provider.