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Fli4l logo cube arcade.gif
Company / developer fli4l-Team
OS family Unix-like
Working state Current
Source model Open source
Initial release 2000
Latest release 3.6.2[1] / September 16, 2012 (2012-09-16)
Latest preview Weekly[2]
Available in German, English, French
Supported platforms i386, x86-64
License GPL (Free software)
Official website www.fli4l.de/en/

fli4l (flexible internet router for linux, before floppy isdn for linux) is a Linux distribution, actively developed by German developers since 2000. The projects main task is to provide a small Linux system that turns almost every machine into a router. The distribution can run from a floppy disk and was created with the aim of simple configuration and support for older hardware.[3][4][5]

fli4l can route between Ethernet and ISDN, DSL or UMTS, or just between Ethernet networks.[4]

Characteristics and requirements[edit]

fli4l is based on the Linux kernel. As the documentation is very extensive no knowledge of Linux is required, however a basic knowledge of network technology is needed.[6]

The hardware requirements for fli4l are low, a 486 with 16 MiB RAM and (depending upon the configuration) one or two network interface controllers is quite adequate. A hard disk drive is not required, but can be used by fli4l too.[7]

Newer versions of fli4l provide also the possibility to create a working installation on a CF card in a card reader, which card then in turn can operate from a CF adapter in an IDE slot. Also the generation of an ISO image is supported to run from a CD-ROM as well as from DOC/DOM for Embedded systems.[7]

fli4l can be configured on Linux, Unix and Windows systems using just text files.[8]

In addition, fli4l has the possibility to encrypt connections over the Internet or via Wireless LAN using OpenVPN or PPTP (Poptop).[9]


There are two development branches for fli4l, a stable and a development version.

The present stable release[1] is based on a 2.6 kernel and contains virtualization by means of Xen. USB and Wireless LAN are supported to a great extent as well as current embedded hardware as ALIX, Soekris and EPIA series.

The development version[2] uses a 3.x.y kernel.

Optional packages[edit]

fli4l is a modular system using so-called OPT-packages. To create an individual configuration, only software packages for those options, that are needed, are downloaded and unzipped into the directory tree. To extend the basic functionality, a wide range of applications is available in the so-called OPT-database;[10] for example, optional packages can be used for monitoring traffic or an fli4l can function as a printserver. This process easily allows own developments, that can be made available to other users via the OPT-database.[10]

Device control[edit]

An fli4l router can be controlled and monitored with a browser-based interface. Besides, the program imonc (isdn monitor client) is available for Windows and Linux (GTK). imonc allows extensive control as well as remote-controlled update of the router's software.[11]


  1. ^ a b Latest stable release, September 22, 2012.
  2. ^ a b Latest weekly development version
  3. ^ "fli4l 3.6.2". Softpedia. undated. Retrieved 28 September 2012. 
  4. ^ a b Haas, Juergen (27 April 2003). "Fli4l (Floppy ISDN/DSL)". About.com. Retrieved 31 March 2012. 
  5. ^ "fli4l". free(code). undated. Retrieved 23 September 2012. 
  6. ^ fli4l documentation: Introduction
  7. ^ a b fli4l documentation: Setup Flavours
  8. ^ fli4l documentation: Configuration
  9. ^ Poptop
  10. ^ a b The fli4l database for additional packages
  11. ^ imonc

Further reading[edit]

External links[edit]