LXD 4.0 - Cluster setup with VMs, MTU setup for VM interfaces

I ran into the following issue and am wondering if this is something I should have known to handle at my end …

I have a LXD 4.0 cluster setup on multiple physical hosts where I have launched both containers and VMs. The cluster has been setup to use fan overlay networking. I am using prebuilt container images from ubuntu:* and VM images from images:* repositories.

The issue I have encountered is that the MTU for the default network interface on the VMs is set to 1500, while the fan overlay network expects it to be 1450 or smaller (unfortunately a straightforward ping test works, so it took me a while to debug this). I verified that the containers seem to have the correct setup … as assume this is something that is being handled during the launch setup.

My question - should the images:* builds be handling this automatically? I am specifically using images:ubuntu/18.04.


Hmm, we should make sure that dnsmasq advertises the correct MTU, if it’s correct in the DHCP packets then there’s not a lot more we can do, but maybe that part isn’t quite correct.

@tomp another hopefully easy thing to take a look at?

Nevermind, I just did it.