Comment 1 for bug 1519090

I have tested this extensively today and did not see this exact behavior. However, when the interface is set to "Auto assign", I saw similar behavior in some cases.

In previous versions of MAAS, having a dynamic range on an unmanaged cluster interface meant that we expect MAAS to use DHCP. Upon migrating to 1.9, those DHCP links became "AUTO" links. Thus we see this regression.

I linked a branch which fixes half of this issue by making unmanaged networks consistent with managed networks. That is, if you assign a static range on an unmanaged network and use AUTO, we will assign out of the static range. If it only has a dynamic range, you will get an error. (you must configure the interface to use DHCP, as this bug implies it was originally, but I suspect it wasn't - due to a migration bug.) If the cluster interface has neither, MAAS will assume it can use the entire subnet (minus any configured routers, etc) for allocation.