container host /etc/network/interfaces

auto lo
iface lo inet loopback
    dns-nameservers 192.168.57.250
    dns-search maas

auto ens3
iface ens3 inet manual
    mtu 1500

auto br-ens3
iface br-ens3 inet static
    gateway 192.168.57.254
    address 192.168.57.101/24
    bridge_ports ens3

source /etc/network/interfaces.d/*.cfg