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On Tue, Mar 10, 2015 at 12:53 AM, Miguel Ángel Ajo <majopela at redhat.com> wrote:

> a) What if the subnet pools go into an external network, so, the gateway is
> predefined and external, we may want to be able to specify it, we could
> assume the convention that we’re going to expect the gateway to be on the
> first IP of the subnet...

In this case, you're not going to ask IPAM for just any subnet.
You're going to tell it exactly what you want.  So, the point is moot
here.

> b) Thinking of an on-link route, the gateway could be a fixed IP (regardless
> of the subnet CIDR), this case is not fully supported now in neutron
> l3-agent now, but I plan to add it on the next cycle [5] (sorry, I’ve been a
> bit slow at this), it’s a very neat standard where you can route RIPE blocks
> as subnets to a physical net without spending any extra IP for the router.

IPAM doesn't care if your gateway is an on-link route outside of the
subnet.  Neutron will not even tell IPAM about such a case.  So, we're
fine here.

Carl