Asterisk is a free telephony software. I’m posting here sample commented configuration files for reference purposes, hoping they will help you get kickstarted if needed.

This config sets up :

• SIP phones (for softphones or harware phones with SIP capabilities)
• Voice mails
• A few test phone numbers
• Forwarding of calls to a SIP provider for outbound and incoming calls (from/to PSTN)

That should be plenty already for a SOHO environment !

Note to French readers : Si votre FAI est Free, cette configuration fonctionne pour passer / recevoir des appels via le SIP de Free (Freephonie).