If you have reached this article thinking “What is Dynagen?” you may well find your life a lot easier after reading this. (Or just look at the videos below for step by step instructions)

To start with I will quickly give you an overview of Dynamips; Dynamips is a Cisco router emulator, not a simulator, and what that means is that you can run a real IOS image and emulate Cisco router hardware within PC software!

Initially Dynamips emulated just the 7200 series but support has now been extended to the 2600, 3600, & 3800 series routers plus a large number of modules/port adapters.  Ethernet and frame-relay switches can also be virtualized (not emulated).

Dynamips brings with it the possibility of training, testing, and POC without requiring actual Cisco hardware!J!

Dynamips as you would imagine is quite a complex application in itself and that’s where Dynagen comes into the equation.  Dynagen is a front-end to Dynamips, the main benefit being that it provides a management CLI.

This article will attempt to cover the basics of Dynagen and also give you a few other useful pointers.  I have made an assumption that you will be running Windows (2000/XP).

Installation:
The software download can be found @ http://dynagen.org, accepting all of the defaults when installing is advised.  Here is a link to a video showing you how to install Dynagen.
*Dynamips requires WinPcap to function

Where to start:
Once you have installed Dynagen three icons should have been placed on your desktop:

         ‘Dynamips Server’
         !=== Used to start the server
         ‘Dynagen Sample Labs’
         !=== Contains example configurations
         ‘Network Device List’
         !=== Used to identify computer interfaces to imitate router interfaces

We will start by using a sample lab to review a basic configuration file and actual startup process.  Double click the newly created ‘Dynagen Sample Labs’ shortcut and then browse into the ‘simple1’ folder, you should find a file named simple1.net.  After install the ‘.net’ extension is registered to the Dynagen application, ‘.net’ files are clear text configuration files that can be edited using a text editor such as notepad or wordpad.  Open the file using notepad:

       

Let’s run through the file:

        [localhost]
        !=== Tells Dynagen the server is running locally (‘Dynamips Server’ icon)

        [[7200]]
        !=== High level configuration options for all 7200 series routers used
        !=== This could also be 2600, 3600, or 3800
        image =
        !=== This is the IOS image location for all same model routers
        !=== This line will more than likely need to be amended to reflect an image you have
        npe =
        !=== ‘Network Processing Engine’ to emulate
        ram =
        !=== RAM to assign to same model routers (can be overridden at lower level)

        [[ROUTER R1]]
        !=== New router created with a name of ‘R1’
        s1/0 = R2 s1/0
        !=== Here a physical interface is mapped to a physical interface of another router
        !=== ‘s1/0’ is the local ‘interface Serial1/0’ and ‘R2 s1/0’ is R2’s ‘interface Serial1/0’
        !=== This line means a virtual back-to-back serial cable will be connected for you

        [[ROUTER R2]]
        !=== New router created with a name of ‘R2’
        !=== Mirror statements for connections are not required
        !=== Router must be created even if no connections statements are specified

Once a configuration file has been created/customized two steps should then be completed; one before launching the lab, and one during.

Before – IOS Image
IOS images in standard form are actually compressed files (you may recall an ‘uncompressing’ message if you have ever watched a bootup), leaving the real IOS image within a compressed file creates a lot of overhead for your PC when it boots up a router in software which increases the router bootup time.  To reduce this time you should open the compressed IOS .bin file with archiving software (e.g. WinRAR) and extract the contents.  It is also good practice to rename the uncompressed file to a less generic name.  Please find a video here, the video shows how an IOS image can be extracted to the Dynagen image directory and then how to update the image location in a .net file – in this case simple1.net.

During – IdlePC
When an IOS image is launched using Dynamips your PC will not be able to differentiate between the router’s ‘real work’ and idle routines and so the router instance will use as much resource as possible, this becomes obvious when your CPU hits 100%.  ‘IdlePC’ is a value set locally that tells your computer when the router is idle or not and therefore when software needs to compute routines.  It is set on a per-IOS image level, not router or host machine level which means values that are known to be good are valid on all dynamips servers.

How to use the Dynagen Management Console
The management console is relatively straight forward to use.  A ‘?’ displays all available commands:
       

A video will follow which will make use of the majority of commands you need to concern yourself with (initially at least).  Here is a list of the main five:

        list
        !=== List all routers and status
        start
        !=== Used to start a router bootup (/all switch = all routers)
        stop
        !=== Used to stop a router (/all switch = all routers)
        console/telnet
        !=== Used to access the router CLI
        idlepc
        !=== Used to configure IdlePC settings

Please find the video here, this video shows you how to launch the example lab and then configure the idlepc value for a given IOS image.


Custom Lab Creation
Here I will run through creating a virtual lab from scratch.  Please click the image to launch the video.

- A three router lab with PA-4T & PA-2FE-TX port adapters installed.       

The topology above has been created entirely in software on one PC!  No need to invest in routers and rack space.  But most important of all - No noise!

What’s next:
In future articles I will cover the following:
        How to capture traffic
        Creating a virtual Ethernet switch (access and trunk ports)
        Creating a virtual frame-relay switch
        The ‘LAN’ option
        Adding a host – Use of Microsoft Loopback Adapter
        Adding a real connection - An interface into the ‘real world’

Other Information/Files:
Please don’t get any ideas about replacing real (production) Cisco hardware with Dynamips, a Cisco router emulated by a PC simply can’t get anywhere near the performance of the real thing.  I also can’t imagine it’s a lawful thing to do.

A router reload should always be performed from within the Dynagen Management Console using the ‘reload’ command and not from the Cisco IOS CLI.

All configuration options can be found @
‘C:\Program Files\Dynamips\sample_labs\all_config_options.txt’

A tutorial file can be found @
‘C:\Program Files\Dynamips\docs\tutorial.htm’

A guide to the minimum RAM to assign to routers:
IOS 12.1 = 48MB
IOS 12.2 = 64MB
IOS 12.3 = 96MB
IOS 12.4 = 128MB

Good IdlePC values to use (can be added to %USERPROFILE%\dynagenidledb.ini – the Dynagen database):
c2691-js-mz.123-21.bin = 0x604bbfa8
c7200-js-mz.123-21.bin = 0x60756088
c3620-is-mz.123-21.bin = 0x603f0940
c7200-js-mz.121-27b.bin = 0x60529f78

Supported Modules:

URL’s:
Dynamips (the emulator)
http://www.ipflow.utc.fr/index.php/Cisco_7200_Simulator

Dynamips Blog
http://www.ipflow.utc.fr/blog/

Dynagui (A GUI Frontend)
http://dynagui.sourceforge.net/

	Visual Video Demonstration of Dynamips/Dynagen - PART 1 How to install on your PC

	Visual Video Demonstration of Dynamips/Dynagen - PART 2 Extracting an IOS and using it

	Visual Video Demonstration of Dynamips/Dynagen - PART 3 Making sure the PC does not run at 100% CPU