Asterisk™ is a complete PBX in software. It runs on Linux and provides all of the features you would expect from a PBX and more. Asterisk™ does voice over IP in three protocols, and can interoperate with almost all standards-based telephony equipment using relatively inexpensive hardware.Asterisk™ is a complete PBX in software. It runs on Linux and provides all of the features you would expect from a PBX and more. Asterisk™ does voice over IP in three protocols, and can interoperate with almost all standards-based telephony equipment using relatively inexpensive hardware.