Open source network simulators/emulators

Recently I came across two open source LAN/WAN simulators , which can very very useful in learning network administration and application testing.

1. GNS3 (http://www.gns3.net/)

GNS3 is a graphical network simulator that allows simulation of complex networks. GNS3 is an excellent complementary tool to real labs for network engineers, administrators and people wanting to pass certifications such as CCNA, CCNP, CCIP, CCIE, JNCIA, JNCIS, JNCIE.

It can also be used to experiment features of Cisco IOS, Juniper JunOS or to check configurations that need to be deployed later on real routers.

This project is an open source, free program that may be used on multiple operating systems, including Windows, Linux, and MacOS X.

Features overview

• Design of high quality and complex network topologies.
• Emulation of many Cisco IOS router platforms, IPS, PIX and ASA firewalls, JunOS.
• Simulation of simple Ethernet, ATM and Frame Relay switches.
• Connection of the simulated network to the real world!
• Packet capture using Wireshark.

Download : http://sourceforge.net/projects/gns-3/ 

2.WANem :The Wide Area Network emulator
( http://wanem.sourceforge.net/ )

WANem is a Wide Area Network Emulator, meant to provide a real experience of a Wide Area Network/Internet, during application development / testing over a LAN environment.