My virt-manager cloned VMs get the same IP on the host

For some reason the host is giving each cloned VM the same IP address, even though the clone gets a new MAC address for its NIC...

Useful commands:

virsh net-list
virsh net-info default
virsh net-dhcp-leases default

virsh list
virsh domifaddr <domain>

virsh net-dumpxml default
virsh dumpxml <domain>

Why? What the flip? The MAC addresses are different! Logging into each box and requesting a new lease only worked temporarily. Something was wrong...

And for the solution see: https://superuser.com/questions/1338510/wrong-ip-address-from-dhcp-client-on-ubuntu-18-04

The lease is given per Client-ID (not per MAC), and Client-ID is derived from /etc/machine-id, and that file is the same on all VMs!

Just tweak /etc/machine-id and reboot. Hey presto, new IPs!

Many thanks to stefanha at irc://irc.oftc.net/#virt