Check out how to configure and test Asterisk by user . Asterisk is an open source PBX system used for VoIP protocols and other call related functions.

Net-VoIP-Asterisk-Topology

Asterisk — Open source PBX system. Developed by Mark Spencer. Working on Linux, FreeBSD, OpenBSD and Solaris operation systems. The project name created from “*”. You can read more about asterisk from http://asterisk.ru/ and http://www.asterisk.org/ official page.

Asterisk have all features which have in any hardware PBX’s. Supports a lots of VoIP protocols.

Features:

  • Voice Mail
  • Conference rooms
  • IVR menu
  • Call handling center(By using different algorithms, define call queueing and distribution to subscribers)
  • Call Detail Record

Full tutorial: http://www.unixmen.com/freebsd-asterisk-test-between-2-extensions/