[Openstack-operators] [neutron] multiple external networks on the same host NIC

Uwe Sauter uwe.sauter.de at gmail.com
Sat Apr 25 20:42:06 UTC 2015

Am 25.04.2015 um 22:28 schrieb Mike Spreitzer:
>> From: Uwe Sauter <uwe.sauter.de at gmail.com>
>> Or instead of using Linux bridges you could use a manually created
>> OpenVSwitch bridge. This allows you to add "internal"
>> ports that could be used by Neutron like any other interface.
>> - Create OVS bridge
>> - Add your external interface to OVS bridge
>>   * If your external connection supports/needs VLANs, configure
>> external interface as trunk
>> - Add any number of internal interfaces to OVS bridge
>>   * Tag each interface with its VLAN ID, if needed
>> - Configure Neutron to use one internal interface for each subnet
>> you'd like to use (no VLAN configuration required as
>> this happenes outside of Neutron)
>> Regards,
>>    Uwe
>> Am 25.04.2015 um 21:41 schrieb George Shuklin:
>> > Can you put them to different vlans? After that it would be very easy task.
>> >
>> > If not, AFAIK, neutron does not allow this.
>> >
>> > Or you can trick it thinking it is (are) separate networks.
>> >
>> > Create brige (br-join), plug eth to it.
>> > Create to fake external bridges (br-ex1, br-ex2). Join them
>> together to br-join by patch links
>> > (http://blog.scottlowe.org/2012/11/27/connecting-ovs-bridges-with-
>> patch-ports/)
>> >
>> > Instruct neutron like there is two external networks: one on br-
>> ex1, second on br-ex2.
>> >
>> > But be alert that this not very stable configuration, you need to
>> maintain it by yourself.
>> >
>> > On 04/25/2015 10:13 PM, Mike Spreitzer wrote:
>> >> Is there a way to create multiple external networks from
>> Neutron's point of view, where both of those networks are
>> >> accessed through the same host NIC?  Obviously those networks
>> would be using different subnets.  I need this sort of
>> >> thing because the two subnets are treated differently by the
>> stuff outside of OpenStack, so I need a way that a tenant
>> >> can get a floating IP of the sort he wants.  Since Neutron
>> equates floating IP allocation pools with external
>> >> networks, I need two external networks.
>> >>
>> >> I found, for example, http://www.marcoberube.com/archives/248---
>> which describes how to have multiple external
>> >> networks but uses a distinct host network interface for each one.
>> >>
>> >> Thanks,
>> >> Mike
> Thanks Uwe, I might try that, it sounds like the simplest thing that will work.  I think I can not use VLAN tagging in my
> environment.  I am using ML2 with OVS, and it is working now with a single external network.  Should I expect to find a
> bridge_mappings entry in my plugin.ini?  I do not find one now.  This setup was mainly created by other people, so I am not sure
> what to expect.  When using ML2 with OVS, how do I tell Neutron what my bridge mappings are?
> Thanks,
> Mike


VLAN is optional in the setup I described. I just was pointing out where such a configuration could take place.

As far as my experience with OVS and Neutron goes, Neutron will just ignore already existing configurations. That's also the
reason why install manuals tell you to create br-int and br-ex.

Regarding the exact configuration of ML2 and plugin.ini I'm not quite sure if I understand your question correctly. Are you asking
how to tell Neutron which interface should be used for the different IP subnets?

Perhaps you could post your plugin.ini with sensitive information replaced with something generic.



More information about the OpenStack-operators mailing list