For the following filename, the letters MZ are the key: The IOS image name will tell you which compression is being used. When using GNS3/Dynagen, you can save startup time by uncompressing the IOS images.Ĭisco IOS images are compressed using one of three formats, zip, mzip or STAC.
As a result, IOS was compressed and the first thing IOS usually does these days on startup is to uncompress the image from Flash to RAM.
Historically, flash memory was expensive and not very large. Working and Unzipping IOS ImagesĬisco IOS images are compressed so as to use the least amount of flash memory. This is becuase the binary that emulates the PIX/ASA has only been compiled for the Windows and Linux platforms. PEMU does not work on MAC OS X (as far as I know and these settings make no difference.). I haven’t used this feature as yet and may post something on this in the future.
