How to set up asterisk for calls within the local network?

Question

Asterisk

You need to set up an asterisk for calls on the local network from androids to each other, without access to the outside. Well, a maximum of twenty people will communicate. Can you recommend a ready config. Thank you!
UPD: I stuck an asterisk on debian 1.8, turned on the web face, but it shows me 403 access denied.

Answer 1

Install FreePBX and set it up in the webmord, knowledge of English at the high school level should be enough.