Will the VOIP work over a private network?

Yes, the VOIP uses the Internet or your private network (Intranet). Any IP data network can route the calls using a technology called Voice over Internet Protocol (VOIP). It doesn't matter if you are using the Internet, a private Intranet, ISDN, DSL, frame relay, wireless, microwave, or satellite for your data communications network, as long as it uses the Internet Protocol (IP).