Comment 4 for bug 1665680

I would recommend using loose-mode reverse path filtering on the MAAS server for now.

Strict reverse path filtering seems like it would make a lot of sense for a border router, but little sense for an internal MAAS server.

But I agree that it makes sense to supply a cloud-config-url (and related URLs) using a directly attached subnet if possible. Right now we use the subnet to select a rack controller, and we use the rack controller to select the appropriate rack-facing subnet on the region. But I like the idea of taking a simpler approach and using an on-subnet IP address if possible.