I’ve just heard about a project called Dynamips – it is apparently a way of booting an IOS image on a PC. Not just simulating IOS – actually booting the binary!
Now of course this isn’t going to function *quite* like a router, so don’t think you can junk your Cisco hardware just yet. According to Brian McGahan of Internetwork Expert, it is advisable to have 2GB of RAM to run the simulator and boot an image.
Elsewhere, I’ve read that performance is not very high. Apparently you can expect 1kpps. To put that in context, the slowest NPE for a 7200 (an NPE-100) can forward in the region of 100Kpps.
Despite these drawbacks, if you are working on your CCNA, CCNP or CCIE and haven’t got enough stuff to build a full rack, this might get you out of a hole.
Of particular interest is that it runs in a so-called “Hypervisor” mode, allows the creation of multiple virtual routers and virtual links between them. The links can be POS, ATM, serial or ethernet.
Have a look at this page for more information.
The Wikipedia page on Dynamips is also good – gives you an example config etc.