Caring for Your Dynamips Install - Deleting Unwanted Files

Dynamips and dynagen are well behaved programs most of the time. Occasionally I am configuring a feature or two that causes IOS to crash (most recently I was configuring MPLS and redistribution on c2600 IOS which got really busted).

Then I noticed that my hard drive didn’t have a lot of free space….

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iTerm and Dynamips - Write to All Terminals at Once

I am often find myself needing to stop, make a configuration change to Dynagen, and then restart. To make sure I don’t miss anything I go to every screen and write the configuration.

In iTerm, there is the ability to send the same command to all screens at once, excellent!

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Suspending and Resuming Dynamips

As someone who travels often, and always looking to make use of the travel time, I was pleased to find that I can suspend and resume the Dynamips routers. This saves me battery on longer trips, or lets me have more CPU when I running other applications such as Parallels / VMware to give me some Microsoft Visio joy. iTerm sessions are not terminated by doing this, they just don’t show any data until you resume the sessions.
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Configuring iTerm for Dynamips

To get started with my lab faster I use iTerm to prepare a full set of possible sessions. This post walks through how to do this which should help you to get started faster. Also some keyboard shortcuts.
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Unzip IOS Images for Dynamips

I have a directory ‘dynalab’ in my ‘Documents’ where I have put ALL my Dynamips / Dynagen related files. I created a directory there which has all my IOS images, this makes more sense to my mind. Makes it easier to backup.

gf:Documents gregferro$ mkdir dynalab
gf:Documents gregferro$ cd dynalab
gf:dynalab gregferro$ ls
gf:dynalab gregferro$

You can copy IOS images as normal using the Finder into the dynalab directory. To uncompress the images you can either download the Zipeg program (use a search engine to find it), or use the command line as follows:

gf:dyncode gregferro$ unzip -p c1700-sy-121-9.bin > c1700-sy-121-9.image
warning [c1700-sy-121-9.bin]: 16304 extra bytes at beginning or within zipfile
(attempting to process anyway)
gf:dyncode gregferro$


I have renamed the IOS file from .bin to .image so I can determine that it has been uncompressed. I keep the rest of the name the same, because that tells me the feature set of the image.

Now your images are ready to use. You can see the script I use to start Dynamips / Dynagen in a earlier post.

Tips for Dynamips / Dynagen on Leopard OS X

I downloaded the most recent Interim relase from the dynagen.org interim builds web site and then got to work in getting it setup.

To help with the scripting and updates I put everything into a directory under my documents folder called
dynalab
. Then I copied the Dynagen directory from the mounted DMG directly to its own directory.

Then I located some IOS code that I liked the look of, and dropped that into its own directory that I call
dyncode
Then I created a directory called
firstlab
and this is where I have created my lab. The directory looks like this:

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Dynamips on a MacBook Pro

I am doing some proof of concept for an MPLS data centre and did something I have not normally done. I used my MacBook Pro to run Dynamips / Dynagen. I am very pleased with 9 3640 routers running Enterprise Plus, and 2 2611 Routers with IP and running less than 60% CPU across both cores

This means that I have still have enough resources to run quite few other programs including Parallels (although it does run a little slow). I have an older MacBook Pro, but upgraded to to 4 GB RAM. I found that the 2 x 2GB RAM modules run faster than 1 x 2Gb (as you might expect) but its a shame that only 3GB can be used or I could have quite a few more.

I won’t repeat what other people have said about Dynamips, but running it on OS X Leopard is very fine indeed.