It's a bit hard to parse a network topology by email, but from a theoretical point of view - you can statically route a /24 towards the external IP of an openstack router from a device upstream.

I do believe there is a BGP component for Openstack but I'm not sure it's role is to dynamically advertised networks from Openstack towards the wider network.

On Thu, Feb 4, 2021 at 11:45 AM <DHilsbos@performair.com> wrote:
All;

My team and I have been working through the tutorials on Server World (server-world.com/ean/), in order to learn and build an OpenStack cluster.  We've also been looking at the official documentation to attempt to increase our knowledge of the subject.

I have a question about Neutron though.  All the examples that I remember have Neutron setup with a single router.  The router is part of a "provider" network, and subnet on the outside, and one or more "tenant" networks on the inside.  Floating IPS, then appear to be IP addresses belonging to the "provider" subnet, that are applied to the router, and which the router then NATs.

These setups look like this:

Physrouter1 (physical router) subnet: 192.168.0.0/24, IP address: 192.168.0.1
|
Physnet1 (192.168.0.0/24)(ovs network definition)
|
Router1 (ovs router)(allocation pool: 192.168.0.100 - 192.168.0.254) <-- Floating IPs are "owned" by this, and are in the range of the allocation pool
|
Tenant network(s)

This has the advantage of being easy, fast, secure, and simple to setup.

What if you wanted something where you could route whole subnet into your OpenStack cluster.

Physrouter1 (physical router) subnet: 172.16.255.0/24, IP address: 172.16.255.1
|
Physnet1 (172.16.255.0/24)(ovs network definition)
|
Router1 (ovs router)(fixed IP addresses: 172.16.255.2 & 172.16.254.1/24 + static / dynamic routing)
|
Network (17216.254.0/24)
|
Router2(ovs router)(allocation pool: 172.16.254.5 - 172.16.254.254) <-- Floating IPs are "owned" by this, and are in the range of the allocation pool
|
Tenant network(s)

Is my understanding accurate?
Are there advantages of one over the other?
What commands are used to specify static IPs for ovs routers, and static routing rules?

Thank you,

Dominic L. Hilsbos, MBA
Director - Information Technology
Perform Air International Inc.
DHilsbos@PerformAir.com
www.PerformAir.com