GNS3 FRR Appliance

In my spare time, what little I have, I’ve been wanting to play with some OSS networking projects. For those playing along at home, during last Suse hackweek I played with wireguard, and to test the environment I wanted to set up some routing.
For which I used FRR.

FRR is a pretty cool project, if brings the networking routing stack to Linux, or rather gives us a full opensource routing stack. As most routers are actually Linux anyway.

Many years ago I happened to work at Fujitsu working in a gateway environment, and started playing around with networking. And that was my first experience with GNS3. An opensource network simulator. Back then I needed to have a copy of cisco IOS images to really play with routing protocols, so that make things harder, great open source product but needed access to proprietary router OSes.

FRR provides a CLI _very_ similar to ciscos, and make we think, hey I wonder if there is an FRR appliance we can use in GNS3?
And there was!!!

When I downloaded it and decompressed the cow2 image it was 1.5GB!!! For a single router image. It works great, but what if I wanted a bunch of routers to play with things like OSPF or BGP etc. Surely we can make a smaller one.

Kiwi

At Suse we use kiwi-ng to build machine images and release media. And to make things even easier for me we already have a kiwi config for small OpenSuse Leap JEOS images, jeos is “just enough OS”. So I hacked one to include FRR. All extra tweaks needed to the image are also easily done by bash hook scripts.

I wont go in to too much detail how because I created a git repo where I have it all including a detailed README: https://github.com/matthewoliver/frr_gns3

So feel free to check that would and build and use the image.

But today, I went one step further. OpenSuse’s Open Build System, which is used to build all RPMs for OpenSuse, but can also build debs and whatever build you need, also supports building docker containers and system images using kiwi!

So have now got the OBS to build the image for me. The image can be downloaded from: https://download.opensuse.org/repositories/home:/mattoliverau/images/

And if you want to send any OBS requests to change it the project/package is: https://build.opensuse.org/package/show/home:mattoliverau/FRR-OpenSuse-Appliance

To import it into GNS3 you need the gns3a file, which you can find in my git repo or in the OBS project page.

The best part is this image is only 300MB, which is much better then 1.5GB!
I did have it a little smaller, 200-250MB, but unfortunately the JEOS cut down kernel doesn’t contain the MPLS modules, so had to pull in the full default SUSE kernel. If this became a real thing and not a pet project, I could go and build a FRR cutdown kernel to get the size down, but 300MB is already a lot better then where it was at.

Hostname Hack

When using GNS3 and you place a router, you want to be able to name the router and when you access the console it’s _really_ nice to see the router name you specified in GNS3 as the hostname. Why, because if you have a bunch, you want want a bunch of tags all with the localhost hostname on the commandline… this doesn’t really help.

The FRR image is using qemu, and there wasn’t a nice way to access the name of the VM from inside the container, and now an easy way to insert the name from outside. But found 1 approach that seems to be working, enter my dodgy hostname hack!

I also wanted to to it without hacking the gns3server code. I couldn’t easily pass the hostname in but I could pass it in via a null device with the router name its id:

/dev/virtio-ports/frr.router.hostname.%vm-name%

So I simply wrote a script that sets the hostname based on the existence of this device. Made the script a systemd oneshot service to start at boot and it worked!

This means changing the name of the FRR router in the GNS3 interface, all you need to do is restart the router (stop and start the device) and it’ll apply the name to the router. This saves you having to log in as root and running hostname yourself.

Or better, if you name all your FRR routers before turning them on, then it’ll just work.

In conclusion…

Hopefully now we can have a fully opensource, GNS3 + FRR appliance solution for network training, testing, and inspiring network engineers.

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