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Tuesday, December 12, 2017


What is Dynamips?

Dynamips (DM) is virtualization software that lets you run the Cisco router operating system - the real Cisco IOS software - on your computer. The general idea is straightforward: you download and install DM, then copy an IOS image onto the same computer. You then configure DM, defining a topology - for example, as in the example on the right. Then you start the virtual routers, and now you have a router lab pod running on your PC.
DM does its work by emulating (acting like) router hardware (CPU, RAM, interfaces, console). The IOS image does not know it is running on a virtual router. The IOS will try to send packets out interfaces; DM will intercept and give those packets to the next virtual router, as if the packet actually flowed over cables. DM can even forward packets out its real LAN interfaces to external devices. You can connect to the console of each virtual router, telnet to the routers, and get access to all the commands supported on the real IOS you installed.
Here are some of the key points about DM:
  • It’s free.
  • It’s popular, with lots of sites at which you can get collaborative help from others that use DM.
  • It uses two other related free packages: Dynagen (which is imbedded in the DM download these days) and GNS3 (an optional graphical front-end).
  • You must supply the IOS image(s).
  • The performance of the software requires some attention and tuning, particularly as you add more routers.
  • DM emulates Cisco routers, but not Cisco switches.


Advantages over Using the CCNA Simulator or Real Gear


  • Potential cost savings – you can avoid buying used routers
  • It can be more convenient to use compared to real gear, particularly when changing topologies frequently. 
  • Portable: install it on a laptop and practice while on the road
  • It runs real IOS, so it supports all commands (whereas Sims do not)
  • Because it runs IOS, it will actually forward packets, even with external devices
  • Not limited to CCNA commands (whereas the Sim supports only CCNA level commands)


I want Dynamips - Now What?

Tons of information exists about how to use DM etc, how to install, make it work on different OS’s, how to make it do different router features, with written docs and videos. So, we're not going to try to replicate that information on this site. The tutorial on the Dynagen site is a good overall place to start.  See links in right margin, and dive in from there!