This wiki is a community-maintained resource about everything there is to know about IPFire.
Most of the installations of IPFire are done by installing it directly on a piece of hardware. However, Virtualization is an alternative where IPFire is installed as a running image, sharing hardware with other running instances. IPFire has been used successfully on the following virtual platforms.
Virtualization allows several virtual servers to run on the same piece of hardware. This is done through a special piece of software known as a Hypervisor. When the physical machine is running, the main process is the hypervisor, which simply controls which virtual machines are temporarily in control.
Many servers spend significant time just sitting around, waiting for something to do. And, in many cases, draw almost as much electricity during that time as they do when very busy. Using virtualization allows you to optimize your cost in equipment, maintenance and operating cost by ensuring your server(s) are operating up to their potential.
Common advantages to virtualization are:
Disadvantages of utilizing virtualization are:
In some cases, you will require a single server with multiple virtuals, all of which may have public IP addresses. You could place a firewall in front of this machine, or simply use create an "all in one" server which contains the content and the firewall.
One possibility is a single physical machine providing web services and also backing up sensitive data from the corporate office. Clearly, you do not want the sensitive data to be on a public facing web/mail server, yet it only makes sense to build one physical machine (and pay one colocation fee). In this case, you could build a virtual web server and a virtual backup server, then add a virtual IPFire firewall on the front end. Access to the web server would be public, but connections to the backup server would be limited to the public IP address of the corporate firewall. This could be set up as a red/orange network in IPFire.
IPFire uses very few resources. It is very possible to build a virtual IPFire instance and, on the same physical server, have a monitoring program (Cacti, Zabbix, Nagios) on the same machine. This consolidates your management functions into one physical machine.
A firewall is very important to your network. If the firewall is unavailable, your entire network may be down. With a virtual firewall, you can snapshot the instance before doing anything configuration changes. If your work gives you an unmanageable result, you can recover from the problems simply by reverting to the snapshot you created.
An even more robust solution would be if you have a shared storage system, such as iSCSI or NFS, which your IPFire block device ("disk drive") is stored on. Most virtualization systems have the ability to rapidly move a running virtual to another physical machine sharing the same block device. Called "migration" in Xen, on a slow network, it can be accomplished with a total downtime of less than 5 seconds. Thus, if you need to perform physical maintenance on a machine, migrate the firewall instance to another machine, perform the necessary work, then migrate it back to the original.
Finally (untested), you can set up DRBD+Heartbeat to create a High Availability firewall, for those places where you absolutely can not have downtime.