Comment 2 for bug 2000325

To reproduce what happens on physical systems I create two VMs with nics in the same bridge on the host. Booting the first VM up and allowing the network config to apply, and then when booting the second VM up layer, as it applies the IPv6 address to the interface in the bridge, the kernel detects a duplicate IPv6 address and networkd fails to configure the interface.

This happens on Focal systemd-networkd, but works fine on Jammy; that is the network configuration is applied (including the duplicate V6) but critically the v4 address and routes are as well.