As making a DMG of GNS3 for Mac OS X using Py2app is a nightmare and has been unsuccessful so far, here are instructions to run GNS3 on your favorite operating system.
Using MRTG with GNS3
February 28th, 2010 by kaage No comments »In this tutorial we’ll use MRTG program to get traffic statistics from emulated routers in GNS3.
How to emulate Cisco ASA
December 4th, 2009 by Jeremy Grossmann 32 comments »In this article, I will show you how to emulate Cisco ASA using Qemu. Once again, please note that ASA is not provided and will not be. So please don’t ask. Also be aware that ASA does not 100% work in Qemu but that’s enough to play with it.
This Howto is still a draft and has been tested only on Linux.
Olive reloaded or how to emulate Juniper routers
October 29th, 2009 by Jeremy Grossmann 84 comments »This article explain you how to emulate Juniper JunOS on a PC using Qemu. This is an updated and enhanced version of excellent howtos from Juniper Clue and Internetwork Pro as well as Himawan Nugroho’s blog. I mainly focused on Qemu, so if you wish to install JunOS on a real PC or using VMware, please have a look at the Juniper Clue article for more information (and of course Google).
So what’s new you would say? First, I chose to use the latest version of Qemu: the 0.11.0 which supports the Intel e1000 network card emulation since version 0.10.0. and includes several fixes for it. I have modified and adapted the old patch for Qemu 0.11.0, it includes the UDP tunnel (connection to Dynamips/GNS3), PCAP and LCAP support. Also, the patch allows multicast traffic with the e1000, i82557b and i82559er Qemu emulated network cards. Moreover, this article show how to emulate JunOS on multiple operating systems: Mac OS X, Windows XP and Linux Ubuntu 9.04 without using an untrustworthy obscure binary downloaded from a forum you can’t even read the language 
» Read more: Olive reloaded or how to emulate Juniper routers