You could configure the sip phones to point directly to one another. No pbx needed. Just “call” and ip address. You only need the pbx to translate/authenticate/provide features. Sip invite comes into phone, making phone ring, pickup phone, and rtp goes directly to phone just like the sip invite. so long as there are no translations causing issues in between, so it actually works best on a private direct network between them.
You could configure the sip phones to point directly to one another. No pbx needed. Just “call” and ip address. You only need the pbx to translate/authenticate/provide features. Sip invite comes into phone, making phone ring, pickup phone, and rtp goes directly to phone just like the sip invite. so long as there are no translations causing issues in between, so it actually works best on a private direct network between them.