GNU Gatekeeper

The GNU Gatekeeper (GnuGk) is a H.323 gatekeeper, available freely under GPL license. It forms the basis for IP telephony (VOIP) or video conferencing systems.

Please read the manual (especially the tutorial) and the FAQ for general information what a gatekeeper does or take a look at some VOIP and H.323 books to get into the subject.

Download GnuGk    Join the community    Get support


The GNU Gatekeeper is very stable. It is being used commercially by many organizations to provide VOIP or video conferencing services.

  • runs on Linux, Windows, MacOS X, Solaris, FreeBSD, OpenBSD and NetBSD
  • can run as a Windows service
  • accounting and call authorization via SQL database, Radius, file or external application
  • database drivers for ODBC, MySQL, MariaDB, PostgreSQL, SQLite and Firebird
  • flexible call routing
  • number rewriting (calling and called)
  • support for NAT traversal (H.460.17, H.460.18, H.460.19, H.460.23 and H.460.24)
  • full H.323 proxy
  • IPv6 support (incl. IPv4-IPv6 conversion)
  • TCP interface for applications
  • CTI functions (eg. VOIP call-center, call transfers)
  • gatekeeper clustering support (neighbors, parent/child, alternates)
  • H.235 security (password authentication and H.235.6 media encryption)
  • LDAP / ActiveDirectory support (H.350 or free form schema)
  • graphical user interface
  • list of supported standards
  • it's free, including source code

There are also lots of ideas for new features.


Please subscribe to the mailinglist to stay up-to-date, discuss the GNU Gatekeeper or ask questions. Please also visit the mailinglist archive.

Professional (paid) support is available directly from the authors of GnuGk. Please contact Jan Willamowius at for more information or use the contact form.

Web Interface

Take a look at the web interface and try the demo. It makes managing the GNU Gatekeeper a lot easier.


The web interface is a commercial add-on to the GNU Gatekeeper. You can order it here.


The interoperability list shows a lot of equipment GnuGk has been used with.

In addition to the general settings explained in the manual there are some specific configuration notes how to configure gateways from some major vendors for use with GnuGk.


Did you know ?

NewsGNU Gatekeeper Blog

17. Aug 2018
GnuGk 5.0 released

GnuGk 5.0 has been released (Download).

5. Apr 2018
GnuGk 4.9 released

GnuGk 4.9 has been released (Download).

10. Oct 2017
Please re-subscribe to the mailinglist

The mailing list is moving and you must re-subscribe to remain on the list.

5. Feb 2015
Nagios Plugin for H.323

New Nagios plugin for H.323 released.

2. Dec 2014
GnuGk Web Interface

The new GnuGk Web Interface is now available.

11. Now 2013
Discussing H.323 encryption

Why your AES encryption probably is worth nothing

25. May 2010
XP Install Video

Video tutorial how to install GnuGk on Windows XP.

17. Sep 2009
Point 9 Meeting

The GnuGk presentation from the Point 9 Meeting is now online.

23. May 2009
H.323 ISDN gateway updated

IsdnGw 0.4.0 is now available.

13. May 2009
GnuGk ACD 1.4 released

A new version of the GnuGk ACD has been released.

5. May 2006
OpenSource Telephony Summit

Here are the slides of the GnuGk talk at the OpenSource Telephony Summit 2006.

3. Aug 2002
Site moved

OpenH323 Gatekeeper moved from to

Last updated: 31. Jul 2018