UDEV contains a default rule triggered early-on which renames all NICs by their index to eX, systemd-udevd subsequently renames the eX interface to ethX. Systemd-udevd can fail to rename the iface if it still has resource locks from the prior renaming which then fails to apply all manner of configurations resulting in a booted zombie which cannot handle L3 traffic. Observed on current branch as of today, with virtio_net, on 6.1.8.