[Openstack] How to support for multiple external networks?

Hauke Bruno Wollentin hauke-bruno.wollentin at innovo-cloud.de
Thu Nov 19 11:27:35 UTC 2015

Hi Ray,

in general it is possible to use two (or more) subnets in one external 
network, but all instances then will get IPs from both subnets (if the 
floating IPs on subnetA are allocated, the next ones will be allocated from 

So you need to create two (non-shared, tenant specific) external networks. For 
the VLAN dedication you could use 1 L3 Agent per 1 external network.


original message
timestamp: Thursday, November 19, 2015 06:18:06 PM
from: Ray Sun <xiaoquqi at gmail.com>
to: openstack at lists.openstack.org
subject: [Openstack] How to support for multiple external networks?
message id: <CAMWzbMdFpGwq315FWQNu7k_gACG1ymiAg3PkG9Krpnd5M9-
CEg at mail.gmail.com>

> I want to setup multiple external networks, but I don't know how to make
> this works.
> Here's my user requirements:
> There are two departments want to use my cloud, but as history problem,
> they wants their VMs to use original IP range. DepA wants to use floating
> ip in, DepB wants to use floating ip in
> I can create multiple subnets in my external network. But I am not quite
> sure if this can work in OpenStack. In my network environment,
> and are two VLANs.
> Anybody know how to implement this kind of scenarios? If this is not
> possible, how can I design my architecture to meet the requirements.
> Thanks.
> Best Regards
> -- Ray
Hauke Bruno Wollentin
(Infrastructure Engineer Cloud)
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