Being the first well-known network device virtualization software, Dynamips is widely used for network labs. In fact, it’s so fixed in people’s awareness that they still think GNS3 = Dynamips, which was the case with GNS3 version 0.8 but hey, we’re on 2.1.11 now. One might wonder, why drop Dynamips if it’s so good that it had survived for so long? Well, I have a few reasons.

It won’t emulate new hardware

Dynamips emulates the hardware; the IOS software thinks that it’s running on a physical Cisco router. However new devices, supporting high-speed data transfer, use ASICs. These custom circuits can’t be emulated on x86 hardware. Even Cisco haven’t tried to do that; the CSR1000V differs from it’s physical brother, the ASR 1001: it doesn’t offer a crypto ASIC, SPA components, QFP, etc. Furthermore, the guys at GNS3 only have resources to maintain the code but not to improve it.

The emulated hardware is old

The Cisco 3700 series routers are in End of Life (EOL) state since 2012. Do you really want to simulate your network with unsupported devices that can’t be purchased anymore? You might say “okay, but I can still use it to learn about networking”. Yes, you’re right but still, why do you want to stick to it? If your computer is not powerful, you can still use IOU or Quagga/FRR; you don’t even have to install them, they’re available as GNS3 appliances.

It will need to be removed

As time goes by, it will be harder and harder to make that old 32 bit code run on modern operating systems. Eventually there will be a condition where no fixes and workarounds will be available and the developers will be forced to drop Dynamips. If you wait until this point, you’ll might have a steep learning curve and you’ll need to put a lot of effort to update your labs. Why don’t you start slowly now, when you can still reach back to Dynamips in case something fails?

There are many other options

All major vendors offer virtual versions of their products; most of them are free to try but there are some free to use alternatives as well. If you want Cisco(ish) CLI, you can use the following:

• Arista vEOS
• BSDRP (runs FRR)
• FRR
• CSR1000V
• IOSv
• IOU (L2 & L3)
• IOS-XRv & IOS-XRv9000
• NX-OSv & NX-OSv9000

If you want to explore other worlds, you can use:

• Juniper vQFX or vMX
• HPE VSR1000v
• VyOS
• Open vSwitch

All the above are available as GNS3 appliances; all you need to do is getting the image files and importing them using the appliance templates from the Marketplace.

Final advice

Dynamips is only a small portion of GNS3’s capabilities. Discover what else this great software can do for you, start using other virtual devices. If you’re stuck? Read the documentation, ask in the forum, or just delete the topology and start over. PS: I posted this article to the GNS3 forum as well.