Cisco Systems corporation names Packet Tracer as a powerful tool for network simulation program allowing network academy students to analyze network behavior gaining learning experience. As a holder of CCNA status and Ubuntu enthusiast I completely agree with above description. See below how to install and run Packet Tracer in your Ubuntu.
Nowadays you can install Packet Tracer in Ubuntu easy way in just a few steps — thankfully to Cisco Packet Tracer is available as binary DEB package for Ubuntu and/or Debian Linux distros.
If you are student of Cisco Network Academy just sign-in and download fresh Packet Tracer DEB package from there (as far as I remember Packet Tracer 5.2 is the latest version). The link should look something like as below. Notice you should find there Linux/Ubuntu version of Packet Tracer instead of binary .exe file for Windows.
Once downloaded install it like any other Ubuntu software:
sudo dpkg -i PacketTracer-5.2-u.i386.deb
After the installation Packet Tracer will appear in Ubuntu menu.
Not a member of Cisco Network Academy Students/Alumni community? Try searching Google for PacketTracer 52 deb for links to binary packages of Packet Tracer for Ubuntu. Here are a few examples:
Once downloaded you have to apply executable bit to .bin file and run it for installation:
chmod +x PacketTracer52_i386_installer-deb.bin
sudo sh PacketTracer52_i386_installer-deb.bin