How does a home router know which connected device is meant to handle a VOIP call? Is there a specific broadcast that is sent out? My home setup uses an analog telephone adapter (ATA) box in bridge mode that handles the calls and I am wondering how the router knows where to send the SIP packets since there is no port forwarding or ALG in use.
I tried disconnecting the ATA and running Wireshark to look for broadcasts being sent to the other devices but nothing showed up; perhaps the router remembers the usual device?
I found a post on another site that mentioned the "registration process" keeping a connection alive, which I assume means the ATA registers the line and from then on out the router only deals with that single connection for all things call-related (SIP, actual call/RTP data, etc.)?
Any information you can provide is appreciated. Thanks.