or if you have not bothered with Step one - [sip:*@pbx.yourdomain.com:*] sip:192.168.1.101:5060
Then click the update button
So registrations that are sent to pbx.yourdomain.com will be forwarded to the internal PBX, and if the username and password is correct, OpenSBC will allow the endpoint to register. Note that the endpoint must be configured with the hostname, e.g. pbx.yourdomain.com, NOT 188.8.131.52
Repeat as necessary for all PBX systems.
This is how the call is actually routed when someone picks up the phone and makes a call.
The syntax here is the same as in step 2 for upper registration, e.g.Edit Route list, and add entries for each of your PBX systems.