Fax server virtualization

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What is server virtualization?

Server virtualization is the term used for the method of running multiple independent applications or operating systems on a single physical machine. It is used as a means of enhancing physical resources to maximize the investment in hardware, where the server administrator uses a software application to divide one physical server into multiple isolated virtual environments.

Server virtualization brings the possibility of sharing hardware between multiple server applications, with each application believing it is running on its own computer with no risk of one application causing another to fail. Disk intensive applications can be matched with CPU heavy ones in order to get the maximum out of each piece of server hardware.

Zetafax's fax virtualization software supports VMware (ESX and ESXi), which can be seen illustrated in the diagram to the right hand side. Zetafax also supports the vSphere Suite and Microsoft Hyper-V.

How fax virtualization works

In a virtualized environment, server applications and their virtualized operating systems access the underlying hardware through a virtualization layer. Communications hardware (such as a fax board) is typically not supported in this virtualized world, and so any server application  that needs to use such hardware requires an alternative approach - this obstacle often results in fax servers being maintained separately from an organisation's virtualized environment. With Fax Over IP (FoIP) this is no longer necessary. Below is an example illustration on how FoIP works:


Fax servers can be deployed in several ways. A common configuration is to connect the fax server directly to the PSTN through an analog or digital (ISDN) telephone line. This is done using fax hardware such as an intelligent fax board, ISDN controller or modem. This is a common setup in smaller organizations, where the fax server simply replaces one or more stand-alone fax machines.


In a virtualized environment, the server applications and their virtualized operating systems access the underlying hardware through a virtualization layer. As communications hardware is typically not supported in this virtualized world, this environment can prove problematic for fax software. Fax over Internet Protocol (FoIP) allows faxes to be transmitted using the IP connection rather than the physical hardware. A software-only device can therefore be implemented on the fax server, which typically integrates with an IP gateway on the network. The gateway is a device, similar to a router, that converts FoIP signals coming from the fax server to fax signals (squeaks) that are transmitted over the PSTN or telephone network.

Download our Zetafax server virtualization datasheet.

Technical diagram

This diagram shows a typical example of a Zetafax server operating in a virtualized environment, communicating via Fax over IP (FoIP). IP-based communication is available to programs running in a virtualized environment, so email servers usually operate without change – though you will need to check the compatibility of your email server with the virtualized server product you have chosen.

As fax servers cannot access fax boards from a virtualized environment, and it is best to switch to using Fax over IP (FoIP) so that the IP connection can be used instead. This brings with it a need to use alternative hardware to connect to the telephone network (PSTN): typically a FoIP-capable internet gateway or IP-based telephone switch (PBX).

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