LXD suddently assigned new IP addresses to all containers

Woke up to complete service outage because all machines on lxdbr0 got a new ip-address - over the last years the DHCP assigned addresses stayed constant so I’m quite surprised that these are not constant anymore.

Nothing in the logs, it probably happened after an auto-update (using snap install on Ubuntu 18.04) I did not change anything on the server.

# snap list lxd
Name  Version  Rev    Aufzeichnung   Herausgeber  Hinweise
lxd   4.0.0    14611  latest/stable  canonical✓   -

but it happened with the refresh to the revision before the current:

# LANG=C snap changes
ID   Status  Spawn                    Ready                    Summary
263  Done    yesterday at 23:19 CEST  yesterday at 23:20 CEST  Automatisch Snap "lxd" auffrischen
264  Done    today at 04:44 CEST      today at 04:45 CEST      Automatisch Snap "lxd" auffrischen

so the refresh at 23:20 was the likely cause.

any ideas why this could happen?

In practice, this IP address change should not happen even if it is just DHCP. The association between container and IP address should be stable because each container gets a random (and unchangeable) Mac address. The DHCP server remembers each association of container and IP address by the MAC address.
Most likely something change there, as if the MAC addresses was reassigned?

There is a way to set the IP address explicitly for each container, using ipv4.address. This means that the DHCP server will be doing static allocation for those containers.

Most likely something change there, as if the MAC addresses was reassigned?

I did not change anything - I wasn’t even logged on. That’s why I think it’s strange. Unfortunatly I don’t have the older data to compare the mac-addresses. I’m trying to find something later today or from backup but there were no changes on the MAC addresses done by me.