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Incoming external subnet routing through a different subnet gateway

Hello!

I'm totally stuck in my tries to figure out how to realize the following scheme:

I have very small amount of external IP addresses ( /29 subnet ). Since I don't want to loose 2 of that IPs just for routing I thought to make a routing with, for ex., 172.16.0.0/30 network and route my external IP subnet through it. Later I'll be able to get another /29 subnet, so I thought to expand this solution for this also.

But I have no idea how to realize it with OpenStack/Neutron. I spent a lot of times in different tries without any success. I tried to make two subnets for external network, but it's impossible to choose which IP to use for external gateway. Even if I would add one subnet (172.16.0.0/30) first and set gateway and then would add an external subnet, the router will use 172.16.0.x for SNAT (as I can understand it).

So I would be very appreciate for any additional advices how to realize this scheme.

I have a multinode setup with separate network node, openvswitch and gre networks.

Incoming external subnet routing through a different subnet gateway

Hello!

I'm totally stuck in my tries to figure out how to realize the following scheme:

I have very small amount of external IP addresses ( /29 subnet ). Since I don't want to loose 2 of that IPs just for routing I thought to make a routing with, for ex., 172.16.0.0/30 network and route my external IP subnet through it. Later I'll be able to get another /29 subnet, so I thought to expand this solution for this also.

But I have no idea how to realize it with OpenStack/Neutron. I spent a lot of times in different tries without any success. I tried to make two subnets for external network, but it's impossible to choose which IP to use for external gateway. Even if I would add one subnet (172.16.0.0/30) first and set gateway and then would add an external subnet, the router will use 172.16.0.x for SNAT (as I can understand it).

So I would be very appreciate for any additional advices how to realize this scheme.

I have a multinode setup with separate network node, openvswitch and gre networks.

Edit: just to make the idea a little bit clearer.

I would like to realise the scheme in which external hardware router interface has IP 172.16.0.1/30, virtual router interface has IP 172.16.0.2/30, hardware router route external public subnet to 172.16.0.2. Virtual external network should has two or more subnets: 172.16.0.0/30 and another (one or more) /29 public subnet. One IP of this public subnet could used as a virtual router SNAT interface and another ones should used as floating IPs.