Download dynamips http://www.ipflow.utc.fr/blog/
Download dynagen http://sourceforge.net/project/showfiles.php?group_id=160317
Copy IOS image into some where like /opt/dynagen/images/
unzip an image for improving the performance
unzip -p urchived_image.bin > extracted_image.image
create an ini file based on simple1.ini
modify this ini file

# dynamips -H 7200 &
# dynagen /opt/dynagen/simple1.net

http://netguide.sakura.ne.jp/dynamips/