Comment 1 for bug 1540512

There may be some synergy between this request and the routed networks work. I wonder if Calico could benefit from the current proposed solution for routed networks. Would it be crazy for Calico to implement enough of the segments API so that the interaction with Nova is the same as with an ML2 or other based plugin? (I suspect it might be)

One difference that I see between this and routed networks is that with the latter, subnets are hard-bound to segments. There really is no flexibility to break the boundary because of the underlying L2 semantics which must be respected. With Calico, I suspect the boundaries are soft. What I mean is that if one cluster of IPs is exhausted, you have the ability to assign an IP from another cluster and route it correctly. It sounds like you want to minimize the fragmentation of IP clusters to keep routing tables concise but you may or may not require absolute adherence to the boundaries. Is that right? Or, do you want the availability of IPs in a cluster to drive placement in Nova?