Today I really wanted to write a deeply technical post (for example, Joe Cozzupoli sent me working configs for QPPB in Inter-AS MPLS VPN environment), but a gem from the SearchNetworking site caught my undistracted attention: they claim the licensing changes introduced in IOS release 15.0 target illicit use of Cisco IOS by Dynamips. The story quotes two of my blogger friends: Stretch and Greg (congratulations to both !!!). Each of them makes very valid points (I am wholeheartedly supporting Stretch’s plea for educational licenses), but somehow the story’s author managed to mix ingredients from their stories to come to a sensational (and totally wrong) conclusion (with a great headline).
Let’s start with the sad fact: Dynamips’ lifeline was cut years ago when Cisco introduced the ISR routers. To run IOS on a completely different mix of hardware, Dynamips has to emulate the router’s hardware, from CPU to every single I/O device. That was “easy” (OK, doable) when Cisco used off-the-shelf components from commodity manufacturers (Motorola, AMD) who publish the detailed specs of their hardware. That tradition was broken in the ISR routers which use I/O chipsets from another manufacturer that gives you data sheets (and in-depth specs) only after signing an NDA agreement (believe me, I’ve tried and got nowhere). That’s why Dynamips supports only the 2600/3600-series and not 2800/3800-series.
The high-end routing products introduced after the 7200 series (and all switches) use customs ASICs. Obviously these are not documented outside of Cisco and thus one cannot emulate them without thorough reverse engineering.
It’s interesting to note that the Dynamips’ author broke no law; he wrote an emulator for publicly known chips. The “only” pirates in the whole story are people who decide to download an IOS image from Cisco and run it on Dynamips (which just “happens” to work just fine). If the Dynamips’ author would start emulating hardware where the specs are only available under NDA or where the emulation requires extensive reverse engineering, he’d be in deep trouble.
With all these limitations in mind, it should surprise no one that you can run IOS release 15.0 in Dynamips only if you use the 7200 images (the IOS support for the x600-series routers was stopped with the release 12.4(15)T). And here comes the fatal bug in the story: IOS licensing was introduced on the ISR-G2 platforms. It is not used (yet) on the high-end boxes and will probably never be used on the 7200 platform. It should be obvious to anyone that this change in IOS deployment model has nothing to do with Dynamips (but then the story would immediately lose all its appeal).