I've asked this question on many other forums and no one seems to know, so that's why I posted in the experts forume. So I just got a new sip phone. It is connected via usb to box A in my bedroom. Box B is in the living room and is running asterisk connected with a Zaptel card to a POTS line. I'm having trouble setting up the phone. Does does box A with the sip phone connected to it need to also be running asterisk? Is there a default asterisk config file for SIP clients? How do I set up box B to be a SIP server to box A? Both box and b sit on the same lan. Any help is appreciated.
If you understand SIP, you should know that any SIP client needs to register to a SIP proxy to make it known to the proxy about its location (IP address, port etc.). Asterisk can act as a SIP proxy. I'm not sure about the exact "sip phone" you mentioned. But if your SIP phone is reachable over the LAN (i.e. has IP address), then you may configure it to register to the Asterisk server on the LAN. Exactly how to configure depends on how you would like to set it up, really.
How did you set up your Asterisk? If you compile and install manually, there is a chance for you to install a set of sample configuration with Asterisk. It would include sip.conf. For SIP, you just have to look into that file for SIP profiles and other related configuration (dtmfmode, jitter buffer, etc.). If your system is AsteriskNow or Trixbox based, they should be there out of the box.
By the way, Asterisk Forums :: Index is likely a better place than here for Asterisk questions.