gns3 packet tracer Netvisualizer ??? diference

Cisco Packet Tracer is sufficient for the CCNA level, but if you could also play with GNS3 you will be more comfortable with real IOS since GNS3 emulates (more than simulates) real routers. The only note against GNS3 is that it can't emulate switches.

 feel confident and comfortable with IOS and routers thanks to GNS3, and with switches and VLANs thanks to Packet Tracer.

to download packettracer
http://www.packettracer.info/packet-tracer-5-3-2-download.html