Can any one help me how to use Dynagen ?
I have all ready installed the software please help me to start the Dynagen...
Firstly Dynamips/Dynagen will only be useful to you if you have access to the relevant Cisco IOS versions to allow you to create and run lab scenarios. Also be aware that Dynamips/Dynagen only emulate Cisco Router hardware. They do not at this point enmulate Cisco Catalyst switches. Though there are some work arounds for this.
If you have access to IOS software, then the tutorial at http://www.dynagen.org is a good place to start for information on how to get up and running with Dynamips/Dynagen.
Another good resource is http://www.blindhog.net/ Here you can find short video tutorials which guide you through different aspects of using Dynamips/Dynagen.
There is also a web forum dedicated to all things to do with Dynamips/Dynagen/GNS3 at hacki.at see http://7200emu.hacki.at/index.php?sid=208a43d6bdad453a4644c4b856cbbbd3
Here you will find lots of information about all things dynamips and people post/share their .net files so you can see how others set up their labs.
There is also GNS3 which is a graphical front end which runs over Dynamips/Dynagen. This can be useful for folks getting started with Dynamips/Dynagen. You use it like creating a network diagram with Visio. You visually build your topology and the program writes the .net file for you. You will find more information here http://www.gns3.net/
Finally for people familiar with Linux, someone has put together a Slax Live CD with Dynamips/Dynagen already installed. You will have to do some configuration to point to your images and working directroy etc, but the report about it are very good. Also Linux appears to be a little better then Windows for running Dynamips/Dynagen (better use of system resources). There is also a Live CD with GNS3. More information can be found here http://www.gns3-labs.com/2008/06/23/dynaslax-dynaslaxgns3-and-dynaslaxusb-livecds/
You can visit the following link... it has some video tutorials that will help you. It also has some topologies :