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How to install Dynamips/Dynagen

Note: tested over Ubuntu 7.04 (Feisty fawn)

Dynamips/Dynagen Installation

Download and install dynamips (CISCO emulator) from For example, for x86 platfoms:

 chmod +x dynamips-0.2.8-RC2-x86.bin
 mv dynamips-0.2.8-RC2-x86.bin /usr/local/bin
 ln -s /usr/local/bin/dynamips-0.2.8-RC2-x86.bin /usr/local/bin/dynamips

Download and install dynagen (the network configuration generator for Dynamips) from For example:

 tar xfvz dynagen-0.10.1.tar.gz
 mv dynagen-0.10.1 /usr/local/
 ln -s /usr/local/dynagen-0.10.1/dynagen /usr/local/bin/

Get a cisco iso image for a router supported by dynamips and copy it to a directory, for example, to vnuml filesystems directory:

 cd /usr/share/vnuml/filesystems
 wget ..../c3640-ik9o3s-mz.124-13a.bin

Unzip the image to accelerate start up:

 unzip -p c3640-ik9o3s-mz.124-13a.bin > c3640-ik9o3s-mz.124-13a.image

And create a simple link for the cisco image:

 ln -s c3640-ik9o3s-mz.124-13a.image c3640

Testing Dynamips/dynagen installation

Start dynamips daemon:

dynamips -H 7200&

Create a simple escenario, for example, copy the following on to a file named


        image = /usr/share/vnuml/filesystems/c3640
        ram = 96

    [[ROUTER R1]]
        model = 3640

Start the scenario with:


Open the router console and wait till the router has started completely:

 console R1

Once started, you have to calculate the best Idle-PC values for your computer, to avoid dynamips consuming all the CPU (if you have a look at your CPU, you will probably see it is 100% occupied).

To estimate the optimum idle pc value for your case, execute:

 idlepc get R1

and choose one of the values marked with an "*". If you see that the CPU usage is not reduced considerably, then execute:

 idlepc show R1

and chose the next value marked with "*".

Repeat the procedure till you find a good value. Then save it with:

 idlepc save R1

The value is copied to the "" file (a line similar to "idlepc = 0x605d32a4"). Remember to add that line to all your routers in your scenarios.