Conference Server

Hi, i just want to configure a conference bridge server, i mean, from remote branches they will connect using sip, and many rooms will have grandstreams phones connecting using sip protocol , so, i will not have any external trunk (no digium hardware, no sip providers ,etc), all will be inside internal network.
Is this scenario even posible?
I just installed freepbx and created a test extension and a conference, but i cant dial to the conference number, sip.conf its empty, and sip show peers gives command not exists error, is that normal?
any help will be appreciated

if you did a clean install asterisk will only load drivers it needs. Once you create a connection to a sip device and it reloads the configuration it should load the drivers needed.

go to the asterisk CLI and type reload. That will force a complete reload and things should be better.

In answer to your question. Sure you can create a internal only server with no external connections. By default that is what you get until you create a external trunk.