networking – Unable to expose a VM host on LAN using libvirt on Ubuntu Server 20.04

I’m seeking help to expose a VM host on my LAN.

I’m using a fresh installation of Ubuntu Server 20.04 on which I installed libvirt and … virt-manager to ease my pain.

The VM is an instance of Home-Assistant, downloaded as a qcow2 image. It is a ResinOS, managing docker containers.

Actually, the VM is up and running. But it is not on my LAN.

My LAN is And my LAN knowledge is …let’s say, uncomplete.

I set the VM to use the bridge that was (probably ?) created when I install libvirt : virbr0 I don’t know where is this virbr0 config : nothing in /etc/network/intefaces

On the Ubuntu Server

    $ip addr 
    3: virbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
    noqueue state UP group default qlen 1000
        link/ether 52:54:00:55:1c:58 brd ff:ff:ff:ff:ff:ff
        inet brd scope global virbr0
           valid_lft forever preferred_lft forever

On the ResinOS guest:

There’re 15 ‘interfaces’ displayed by ip addr, among them :

    enp0s3: inet brd
    hassio: inet brd

My goal is to set hassio on my LAN.

The DHCP server is in my Internet box/Router

Thank you for your help