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

Uwe Sauter uwe.sauter.de at gmail.com
Mon Apr 27 17:22:35 UTC 2015

>> if I understood Georges answer correctly he suggested one bridge
>> (br-join, either OVS or linux bridge) to connect other bridges
>> via patch links, one for each external network you'd like to create.
>> These second level bridges are then used for the Neutron
>> configuration:
>>                 br-ext1 -> Neutron
>>                /
>>             patch-link
>>              /
>> ethX –br-join
>>              \
>>             patch-link
>>                \
>>                 br-ext2 -> Neutron
>> I suggested to use an OVS bridge because there it'd be possible to
>> stay away from the performance-wise worse patch-links and Linux
>> bridges and use "internal" interfaces to connect to Neutron directly
>> – which on second thought won't work if Neutron expects a
>> bridge in that place.
>> What I suggested later on is that you probably don't need any second
>> level bridge at all. Just create a second/third external
>> network with appropriate CIDR. As long as those networks are
>> externally connected to your interface (and thus the bridge) you
>> should be good to go.
> In parallel emails we have established that I have to do what you have drawn.  I need to do that the node(s) that run L3
> agents.  Do I need to modify the bridge_mappings, flat_networks, or network_vlan_ranges configuration statement on the
> other nodes (compute hosts)?
> Thanks,
> Mike

I think you just need to create the cascading bridges with their inter-connects, then tell Neutron the association
between secondary bridge (e.g. br-ext1, br-ext2) and external network. Then create (!) the external networks and restart

Concerning you intra-cloud networking I don't think you need to reconfigure anything as long as this is already working.
Compute hosts shouldn't be affected as its not their business to know about external networks.



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