2 machines with bridge devices and same mac problem

You’re using systemd, maybe you have cockpit installed and are creating a bridge on each host because you need them for libvirt virtual machines.

One machine is your old workstation and you copied the filesystem to the new machine.

But when you create a bridge you local machine suddenly receives the same IP your old machine has received.
You search around, “How do I set a new MAC address on a bridge?”
But none of the answers work.

Then you remember, “Hey, systemd uses machine-id for each machine”.
And indeed it does.

  1. You have to rm -f /etc/machine-id and dbus-uuidgen --ensure=/etc/machine-id
  2. Reboot the system
  3. Recrete the bridge
  4. -id