This will be the first time that we:

• Have a mon running in a different subnet
• Have a mon running bullseye (if we reimage)

So we will want to be careful.

The new IP would be (next free one in https://netbox.wikimedia.org/ipam/prefixes/553/ip-addresses/):

10.64.149.20/24

Things in puppet that might need changing:

• hieradata/role/codfw/wmcs/openstack/eqiad1/backups.yaml
• hieradata/eqiad/profile/cloudceph/mon.yaml

We don't have either a cookbook to rebuild a mon, this might be a good opportunity to create it and test it (including adding functional tests).

This is not so simple, changing the IP of a mon is something absolutely not recommended by upstream:

https://docs.ceph.com/en/latest/rados/operations/add-or-rm-mons/#changing-a-monitor-s-ip-address

Investigating the best way to proceed.