Network Openstack

Using multiple external networks in OpenStack Neutron

This document talks about the reference implementation.

Starting on Icehouse release, a single neutron network node using ML2+ovs or OVS, can handle several external networks. I haven’t found a lot of documentation about it, but basically, here’s how to do it, assuming this: you start from a single external network, which is connected to ‘br-ex’‘  you want to attach the new external network to ‘‘eth1’. In the network node (were neutron-l3-agent, neutron-dhcp-agent, etc.. run): Create a second OVS bridge, which will provide connectivity to the new external network:

ovs-vsctl add-br br-eth1
ovs-vsctl add-port br-eth1 eth1
ip link set eth1 up

(Optionally) If you want to plug a virtual interface into this bridge and add a local IP on the node to this network for testing:

ovs-vsctl add-port br-eth1 vi1 -- set Interface vi1 \ 
ip addr add dev vi1

Edit your /etc/neutron/l3_agent.ini , and set/change:

gateway_external_network_id =
external_network_bridge =

This change tells the l3 agent that it must relay on the physnet<->bridge mappings at /etc/neutron/plugins/openvswitch/ovs_neutron_plugin.ini it will automatically patch those bridges and router interfaces around. For example, in tunneling mode, it will patch br-int to the external bridges, and set the external ‘‘q’‘router interfaces on br-int. Edit your /etc/neutron/plugins/openvswitch/ovs_neutron_plugin.ini to map ‘‘logical physical nets’ to ‘‘external bridges’

bridge_mappings = physnet1:br-ex,physnet2:br-eth1

Restart your neutron-l3-agent and your neutron-openvswitch-agent

neutron net-create ext_net \
            --provider:network_type flat \
            --provider:physical_network physnet1 \

neutron net-create ext_net2 \
                    --provider:network_type flat \
                    --provider:physical_network physnet2 \

And for example create a couple of internal subnets and routers:

And for example create a couple of internal subnets and routers:

# for the first external net
neutron subnet-create ext_net \
          --gateway \

# here the allocation pool goes explicit. all the IPs available..
neutron router-create router1
neutron router-gateway-set router1 ext_net
neutron net-create privnet
neutron subnet-create privnet \
                 --gateway \
                 --name privnet_subnet
neutron router-interface-add router1 privnet_subnet

# for the second external net
neutron subnet-create ext_net2 \
  --allocation-pool start=,end= \
  --gateway= --enable_dhcp=False
neutron router-create router2
neutron router-gateway-set router2 ext_net2
neutron net-create privnet2
neutron subnet-create privnet2 --gateway --name privnet2_subnet
neutron router-interface-add router2 privnet2_subnet

By ajo

Network virtualizer, OpenStack coder, Electronics designer. Learning parent. Novice musician, photographer and woodworker.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.