Hi@calvin2021y. Thanks for getting in touch. Firecracker does not supporttun devices, at the moment. We only handle L2 devices.

is tun device doable ?

virtio-net is a L2 device, hence we tap instead of tun. I guess wecould do tun but this would need us to process the frame in Firecracker before passing it over to the tun device. I would expect that to be slower than what the kernel is able to do. Would you mind me asking what is your use-case, in other words, why tap device doesn't work for you?