Simulating Cisco and Linux Networks

The benefits of designing and testing complex networks in simulated environments are obvious to network professionals and companies. It lets them test the network configurations before implementing it in the real world, and the good thing is that, they can do this without investing any money in expensive hardwares. Virtual networks are also excellent tools for academic and certification purposes like CCNA, CCNP or CCIE, where students can get hands-on experience configuring cisco routers.

Currently Cisco is the leader in Networking market, and Linux, the leader in Server market. So, if you want to test your complex (or not so complex) network configurations before buying any actual linux servers or the very expensive cisco routers, then you can use Dynamips to simulate Cisco Router/Switch and VNUML (Virtual Network User Mode Linux) to simulate your linux servers/routers. Both Dynamips and VNUML are open source and free.

Dynamips

Dynamips is a Cisco router emulator. It’s different from other router simulators in a sense that it doesn’t try to simulate the cisco IOS but loads and runs the real Cisco IOS. The software simulates the cisco router’s hardware, which then becomes capable of booting real cisco IOS. The goals of Dynamips are:

*To be used as a training platform, with software used in real world. It would allow people to become more familiar with Cisco devices, Cisco being the world leader in networking technologies ;
*Test and experiment the numerous and powerful features of Cisco IOS ;
* Check quickly configurations to be deployed later on real routers.

If you want to use Dynamips, then it’s recommended to be used together with Dynagen, which is an user-friendly front-end for the Dynamips cisco router emulator. It uses a simple INI like configuration file to define the routers, switches and networks. You can download Dynagen for Linux, Windows or OS X (the package already includes Dynamips). The Dynagen installation includes very useful Tutorial and sample labs.

Dynamips loading Cisco IOS

VNUML

VNUML is a virtualization tool based on User Mode Linux virtualization software, initially developed to simulate IPv6 scenarios based on Linux and zebra routing daemon. It’s also a very useful tool in simulating general Linux based network scenarios.

VNUML is aimed to help in testing network applications and services over complex testbeds made of several nodes (even tens) and networks inside one Linux machine, without involving the investment and management complexity needed to create it using real equipment.

To use VNUML tool you need VNUML language for describing simulations in XML, and an interpreter of the language (vnumlparser.pl), that builds and manages the simulation, hiding all UML complex details to the user. It is available in package format for .deb based Linux distributions like Debian, Ubuntu, and in source format for other distributions. VNUML Live DVD makes it possible to try VNUML without installing anything into your computer. Here are some useful documentaions: Installation guide, Tutorial and Example Scenarios. This VNUML and Dynamips/Dynagen mixed scenario is quite interesting because it simulates cisco router using Dynamips/Dynagen and Linux Servers using VNUML.

Simple VNUML Description