You you tired of those ###### across your screen? Every time you boot up your router you’ve seen these go across the screen. Many of the Cisco IOSs are compressed. When you see the ####### going across the screen, the IOS is uncompressing itself.
You can save time if you uncompress the image now, and then load the uncompressed image when you start your routers. I would recommend that you uncompress all of your IOS images that you plan to use with GNS3. This will significantly speed up your start up time. As a side note, 2600 series images must be uncompressed before using them. If you do not, they are more likely to crash on you.
Uncompressing on Windows
Here I will show you how easy it is to uncompress IOS with 7-Zip. Right-click on your compressed IOS image and then choose 7-Zip, Extract here. Your uncompressed IOS image will appear, note the size which should be much more than the compressed IOS.
Afterwards rename the extracted file with the same filename as the original except with an extension of image instead of bin. This will help you keep track of which image is uncompressed.
Then within GNS3 choose IOS images and hypervisors under the Edit menu. Choose the uncompressed version of your IOS when you choose an Image file under Settings.
Uncompressing on Mac OS X
In the same way as Windows, many programs can extract IOS on Mac OS X. One of them is Zipeg, find your compress IOS, do a right-click, then ‘Open with’, ‘Other’ and find your installed Zipeg Application.
Now drap the uncompressed IOS to your chosen location on your system and rename the extracted file with the same filename as the original except with an extension of image instead of bin. Other extract softwares should work the same.
Uncompressing on Linux
On Linux you can use unzip which you can easilly install if not already installed.
$ 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)