At the time of this writing, the current version of GNS3 is 0.7.4. Therefore, we will be installing version 0.7.4. Version 0.8.1 is currently in Beta. I just got my MBP 13″ a yesterday, and decided to install GNS3.
1. You can download GNS3 from here http://www.gns3.net/download
2. Double click the .dmg file and drag and drop the GNS3.app into your Application folder. Once you put a copy of GNS3 to the application folder, you should be able to open GNS3. See Figure 1.
3. Now, the Dynamips will fail; therefore, you would need to map it. Open GNS3->Preferences->Dynamips->Executable path:. Then click the browse option and locate the the right dynamips for your system. I have a x64 MBP, so make sure that you select the right one. See Figure 2.
4. Once you have selected the Dynamips, click Test and should say “Dynamips successfully started”.
At this point you should be able to use GNS3 on your Mac.