IP PBX or Internet Protocol Private Branch eXchange is an enterprise-based IP data network device that switches VoIP telephone traffic similar to the way a traditional PBX that switches normal telephone calls. An IP PBX delivers dial-tone to phone extensions, the ability to conference, transfer, and dial other extension number as well as many other features. Voice transmissions are sent via data packets over a data network instead of the traditional phone network.

Many IP PBX products are offered as software for installation on standard-based servers. Some are distributed under open-source licenses. Asterisk is the best known open-source IP PBX.

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