There is an option to update subnet of the external network that will be exclude IPs that are currently in use

[Toni Freger]

During the verification of this RFE [1] I've encountered improper behavior.

When the subnet update is decreasing the number of IP's in the range, and FloatingIp is already in use, the update succeeds and the
excluded FloatingIp continue to function.

From the customer point of view I am also thinking that in the current situation the update should have failed.

[1] https://bugs.launchpad.net/neutron/+bug/1111572

[Kevin Benton (kevinbenton)]

I think this behavior is probably preferred. There should be a away for the admin to update the allocation pool to affect future allocations. We don't want it to break existing floating IPs.

If the admin wants to get ride of allocations outside of the pool, he/she can then go delete them manually.

[Toni Freger (tfreger)]

I think it should be similar to relations between network and instance.
When instance attached to some network admin can't delete the network.

In addition I understand that most of the admins won't decrease the range, but for those rare situation I think there should be at least some warning.