IPFire is an Open Source firewall distribution for x86 and ARM-based systems. It turns the Raspberry Pi computer into a small router for home networks and very small businesses. As the Raspberry Pi computer comes with only one NIC, it works perfectly as a 3G router without plugging in additional hardware.
The generally small system that provides essential services for networks can be enhanced by addons which add new features to IPFire. So the system can be turned into a file server and much more.