Packet Tracer is a complete solution for network simulation and analysis, with which you can simulate the operation of a physical, wireles or fiber network and monitor data packets. simply unavailable to professionals, teachers and students.
The program is part of the Cisco Networking Academy (CCNA) global network teaching and learning software. Packet Tracer's innovative features, including powerful simulation, visualization, creation, assessment, collaboration and capabilities, will help students and teachers collaborate, solve problems, and learn concepts in an engaging and dynamic social environment.
For me, fired the best program for making network diagrams. Interestingly though it is natively for Windows it runs on WINE very well without any bugs.