======================================
Using DevStack with neutron Networking
======================================

This guide will walk you through using OpenStack neutron with the ML2
plugin and the Open vSwitch mechanism driver.


.. _single-interface-ovs:

Using Neutron with a Single Interface
=====================================

In some instances, like on a developer laptop, there is only one
network interface that is available. In this scenario, the physical
interface is added to the Open vSwitch bridge, and the IP address of
the laptop is migrated onto the bridge interface. That way, the
physical interface can be used to transmit self service project
network traffic, the OpenStack API traffic, and management traffic.


.. warning::

    When using a single interface networking setup, there will be a
    temporary network outage as your IP address is moved from the
    physical NIC of your machine, to the OVS bridge. If you are SSH'd
    into the machine from another computer, there is a risk of being
    disconnected from your ssh session (due to arp cache
    invalidation), which would stop the stack.sh or leave it in an
    unfinished state. In these cases, start stack.sh inside its own
    screen session so it can continue to run.


Physical Network Setup
----------------------

In most cases where DevStack is being deployed with a single
interface, there is a hardware router that is being used for external
connectivity and DHCP. The developer machine is connected to this
network and is on a shared subnet with other machines.  The
`local.conf` exhibited here assumes that 1500 is a reasonable MTU to
use on that network.

.. image:: /assets/images/neutron-network-1.png
   :alt: Network configuration for a single DevStack node


DevStack Configuration
----------------------

The following is a complete `local.conf` for the host named
`devstack-1`. It will run all the API and services, as well as
serving as a hypervisor for guest instances.

::

        [[local|localrc]]
        HOST_IP=172.18.161.6
        SERVICE_HOST=172.18.161.6
        MYSQL_HOST=172.18.161.6
        RABBIT_HOST=172.18.161.6
        GLANCE_HOSTPORT=172.18.161.6:9292
        ADMIN_PASSWORD=secret
        DATABASE_PASSWORD=secret
        RABBIT_PASSWORD=secret
        SERVICE_PASSWORD=secret

        ## Neutron options
        Q_USE_SECGROUP=True
        FLOATING_RANGE="172.18.161.0/24"
        IPV4_ADDRS_SAFE_TO_USE="10.0.0.0/22"
        Q_FLOATING_ALLOCATION_POOL=start=172.18.161.250,end=172.18.161.254
        PUBLIC_NETWORK_GATEWAY="172.18.161.1"
        PUBLIC_INTERFACE=eth0

        # Open vSwitch provider networking configuration
        Q_USE_PROVIDERNET_FOR_PUBLIC=True
        OVS_PHYSICAL_BRIDGE=br-ex
        PUBLIC_BRIDGE=br-ex
        OVS_BRIDGE_MAPPINGS=public:br-ex


Adding Additional Compute Nodes
-------------------------------

Let's suppose that after installing DevStack on the first host, you
also want to do multinode testing and networking.

Physical Network Setup
~~~~~~~~~~~~~~~~~~~~~~

.. image:: /assets/images/neutron-network-2.png
   :alt: Network configuration for multiple DevStack nodes

After DevStack installs and configures Neutron, traffic from guest VMs
flows out of `devstack-2` (the compute node) and is encapsulated in a
VXLAN tunnel back to `devstack-1` (the control node) where the L3
agent is running.

::

    stack@devstack-2:~/devstack$ sudo ovs-vsctl show
    8992d965-0ba0-42fd-90e9-20ecc528bc29
        Bridge br-int
            fail_mode: secure
            Port br-int
                Interface br-int
                    type: internal
            Port patch-tun
                Interface patch-tun
                    type: patch
                    options: {peer=patch-int}
        Bridge br-tun
            fail_mode: secure
            Port "vxlan-c0a801f6"
                Interface "vxlan-c0a801f6"
                    type: vxlan
                    options: {df_default="true", in_key=flow, local_ip="172.18.161.7", out_key=flow, remote_ip="172.18.161.6"}
            Port patch-int
                Interface patch-int
                    type: patch
                    options: {peer=patch-tun}
            Port br-tun
                Interface br-tun
                    type: internal
        ovs_version: "2.0.2"

Open vSwitch on the control node, where the L3 agent runs, is
configured to de-encapsulate traffic from compute nodes, then forward
it over the `br-ex` bridge, where `eth0` is attached.

::

    stack@devstack-1:~/devstack$ sudo ovs-vsctl show
    422adeea-48d1-4a1f-98b1-8e7239077964
        Bridge br-tun
            fail_mode: secure
            Port br-tun
                Interface br-tun
                    type: internal
            Port patch-int
                Interface patch-int
                    type: patch
                    options: {peer=patch-tun}
            Port "vxlan-c0a801d8"
                Interface "vxlan-c0a801d8"
                    type: vxlan
                    options: {df_default="true", in_key=flow, local_ip="172.18.161.6", out_key=flow, remote_ip="172.18.161.7"}
        Bridge br-ex
            Port phy-br-ex
                Interface phy-br-ex
                    type: patch
                    options: {peer=int-br-ex}
            Port "eth0"
                Interface "eth0"
            Port br-ex
                Interface br-ex
                    type: internal
        Bridge br-int
            fail_mode: secure
            Port "tapce66332d-ea"
                tag: 1
                Interface "tapce66332d-ea"
                    type: internal
            Port "qg-65e5a4b9-15"
                tag: 2
                Interface "qg-65e5a4b9-15"
                    type: internal
            Port "qr-33e5e471-88"
                tag: 1
                Interface "qr-33e5e471-88"
                    type: internal
            Port "qr-acbe9951-70"
                tag: 1
                Interface "qr-acbe9951-70"
                    type: internal
            Port br-int
                Interface br-int
                    type: internal
            Port patch-tun
                Interface patch-tun
                    type: patch
                    options: {peer=patch-int}
            Port int-br-ex
                Interface int-br-ex
                    type: patch
                    options: {peer=phy-br-ex}
        ovs_version: "2.0.2"

`br-int` is a bridge that the Open vSwitch mechanism driver creates,
which is used as the "integration bridge" where ports are created, and
plugged into the virtual switching fabric. `br-ex` is an OVS bridge
that is used to connect physical ports (like `eth0`), so that floating
IP traffic for project networks can be received from the physical
network infrastructure (and the internet), and routed to self service
project network ports.  `br-tun` is a tunnel bridge that is used to
connect OpenStack nodes (like `devstack-2`) together. This bridge is
used so that project network traffic, using the VXLAN tunneling
protocol, flows between each compute node where project instances run.

DevStack Compute Configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The host `devstack-2` has a very minimal `local.conf`.

::

    [[local|localrc]]
    HOST_IP=172.18.161.7
    SERVICE_HOST=172.18.161.6
    MYSQL_HOST=172.18.161.6
    RABBIT_HOST=172.18.161.6
    GLANCE_HOSTPORT=172.18.161.6:9292
    ADMIN_PASSWORD=secret
    MYSQL_PASSWORD=secret
    RABBIT_PASSWORD=secret
    SERVICE_PASSWORD=secret

    ## Neutron options
    PUBLIC_INTERFACE=eth0
    ENABLED_SERVICES=n-cpu,rabbit,q-agt,placement-client

Network traffic from `eth0` on the compute nodes is then NAT'd by the
controller node that runs Neutron's `neutron-l3-agent` and provides L3
connectivity.


Neutron Networking with Open vSwitch and Provider Networks
==========================================================

In some instances, it is desirable to use neutron's provider
networking extension, so that networks that are configured on an
external router can be utilized by neutron, and instances created via
Nova can attach to the network managed by the external router.

For example, in some lab environments, a hardware router has been
pre-configured by another party, and an OpenStack developer has been
given a VLAN tag and IP address range, so that instances created via
DevStack will use the external router for L3 connectivity, as opposed
to the neutron L3 service.

Physical Network Setup
----------------------

.. image:: /assets/images/neutron-network-3.png
   :alt: Network configuration for provider networks

On a compute node, the first interface, eth0 is used for the OpenStack
management (API, message bus, etc) as well as for ssh for an
administrator to access the machine.

::

        stack@compute:~$ ifconfig eth0
        eth0      Link encap:Ethernet  HWaddr bc:16:65:20:af:fc
                  inet addr:10.0.0.3

eth1 is manually configured at boot to not have an IP address.
Consult your operating system documentation for the appropriate
technique. For Ubuntu, the contents of `/etc/network/interfaces`
contains:

::

        auto eth1
        iface eth1 inet manual
                up ifconfig $IFACE 0.0.0.0 up
                down ifconfig $IFACE 0.0.0.0 down

The second physical interface, eth1 is added to a bridge (in this case
named br-ex), which is used to forward network traffic from guest VMs.

::

        stack@compute:~$ sudo ovs-vsctl add-br br-ex
        stack@compute:~$ sudo ovs-vsctl add-port br-ex eth1
        stack@compute:~$ sudo ovs-vsctl show
        9a25c837-32ab-45f6-b9f2-1dd888abcf0f
            Bridge br-ex
                Port br-ex
                    Interface br-ex
                        type: internal
                Port phy-br-ex
                    Interface phy-br-ex
                        type: patch
                        options: {peer=int-br-ex}
                Port "eth1"
                    Interface "eth1"


Service Configuration
---------------------

**Control Node**

In this example, the control node will run the majority of the
OpenStack API and management services (keystone, glance,
nova, neutron)


**Compute Nodes**

In this example, the nodes that will host guest instances will run
the ``neutron-openvswitch-agent`` for network connectivity, as well as
the compute service ``nova-compute``.

DevStack Configuration
----------------------

.. _ovs-provider-network-controller:

The following is a snippet of the DevStack configuration on the
controller node.

::

        HOST_IP=10.0.0.2
        SERVICE_HOST=10.0.0.2
        MYSQL_HOST=10.0.0.2
        RABBIT_HOST=10.0.0.2
        GLANCE_HOSTPORT=10.0.0.2:9292
        PUBLIC_INTERFACE=eth1

        ADMIN_PASSWORD=secret
        MYSQL_PASSWORD=secret
        RABBIT_PASSWORD=secret
        SERVICE_PASSWORD=secret

        ## Neutron options
        Q_USE_SECGROUP=True
        ENABLE_TENANT_VLANS=True
        TENANT_VLAN_RANGE=3001:4000
        PHYSICAL_NETWORK=default
        OVS_PHYSICAL_BRIDGE=br-ex

        Q_USE_PROVIDER_NETWORKING=True

        disable_service q-l3

        ## Neutron Networking options used to create Neutron Subnets

        IPV4_ADDRS_SAFE_TO_USE="203.0.113.0/24"
        NETWORK_GATEWAY=203.0.113.1
        PROVIDER_SUBNET_NAME="provider_net"
        PROVIDER_NETWORK_TYPE="vlan"
        SEGMENTATION_ID=2010
        USE_SUBNETPOOL=False

In this configuration we are defining IPV4_ADDRS_SAFE_TO_USE to be a
publicly routed IPv4 subnet. In this specific instance we are using
the special TEST-NET-3 subnet defined in `RFC 5737 <https://tools.ietf.org/html/rfc5737>`_,
which is used for documentation.  In your DevStack setup, IPV4_ADDRS_SAFE_TO_USE
would be a public IP address range that you or your organization has
allocated to you, so that you could access your instances from the
public internet.

The following is the DevStack configuration on
compute node 1.

::

        HOST_IP=10.0.0.3
        SERVICE_HOST=10.0.0.2
        MYSQL_HOST=10.0.0.2
        RABBIT_HOST=10.0.0.2
        GLANCE_HOSTPORT=10.0.0.2:9292
        ADMIN_PASSWORD=secret
        MYSQL_PASSWORD=secret
        RABBIT_PASSWORD=secret
        SERVICE_PASSWORD=secret

        # Services that a compute node runs
        ENABLED_SERVICES=n-cpu,rabbit,q-agt

        ## Open vSwitch provider networking options
        PHYSICAL_NETWORK=default
        OVS_PHYSICAL_BRIDGE=br-ex
        PUBLIC_INTERFACE=eth1
        Q_USE_PROVIDER_NETWORKING=True

Compute node 2's configuration will be exactly the same, except
``HOST_IP`` will be ``10.0.0.4``

When DevStack is configured to use provider networking (via
``Q_USE_PROVIDER_NETWORKING`` is True) -
DevStack will automatically add the network interface defined in
``PUBLIC_INTERFACE`` to the ``OVS_PHYSICAL_BRIDGE``

For example, with the above  configuration, a bridge is
created, named ``br-ex`` which is managed by Open vSwitch, and the
second interface on the compute node, ``eth1`` is attached to the
bridge, to forward traffic sent by guest VMs.

Miscellaneous Tips
==================

Non-Standard MTU on the Physical Network
----------------------------------------

Neutron by default uses a MTU of 1500 bytes, which is
the standard MTU for Ethernet.

A different MTU can be specified by adding the following to
the Neutron section of `local.conf`. For example,
if you have network equipment that supports jumbo frames, you could
set the MTU to 9000 bytes by adding the following

::

    [[post-config|/$Q_PLUGIN_CONF_FILE]]
    global_physnet_mtu = 9000


Disabling Next Generation Firewall Tools
----------------------------------------

DevStack does not properly operate with modern firewall tools.  Specifically
it will appear as if the guest VM can access the external network via ICMP,
but UDP and TCP packets will not be delivered to the guest VM.  The root cause
of the issue is that both ufw (Uncomplicated Firewall) and firewalld (Fedora's
firewall manager) apply firewall rules to all interfaces in the system, rather
then per-device.  One solution to this problem is to revert to iptables
functionality.

To get a functional firewall configuration for Fedora do the following:

::

         sudo service iptables save
         sudo systemctl disable firewalld
         sudo systemctl enable iptables
         sudo systemctl stop firewalld
         sudo systemctl start iptables


To get a functional firewall configuration for distributions containing ufw,
disable ufw.  Note ufw is generally not enabled by default in Ubuntu.  To
disable ufw if it was enabled, do the following:

::

        sudo service iptables save
        sudo ufw disable

Configuring Extension Drivers for the ML2 Plugin
------------------------------------------------

Extension drivers for the ML2 plugin are set with the variable
``Q_ML2_PLUGIN_EXT_DRIVERS``, and includes the 'port_security' extension
by default. If you want to remove all the extension drivers (even
'port_security'), set ``Q_ML2_PLUGIN_EXT_DRIVERS`` to blank.


Using Linux Bridge instead of Open vSwitch
------------------------------------------

The configuration for using the Linux Bridge ML2 driver is fairly
straight forward. The Linux Bridge configuration for DevStack is similar
to the :ref:`Open vSwitch based single interface <single-interface-ovs>`
setup, with small modifications for the interface mappings.


::

    [[local|localrc]]
    HOST_IP=172.18.161.6
    SERVICE_HOST=172.18.161.6
    MYSQL_HOST=172.18.161.6
    RABBIT_HOST=172.18.161.6
    GLANCE_HOSTPORT=172.18.161.6:9292
    ADMIN_PASSWORD=secret
    DATABASE_PASSWORD=secret
    RABBIT_PASSWORD=secret
    SERVICE_PASSWORD=secret

    ## Neutron options
    Q_USE_SECGROUP=True
    FLOATING_RANGE="172.18.161.0/24"
    IPV4_ADDRS_SAFE_TO_USE="10.0.0.0/24"
    Q_FLOATING_ALLOCATION_POOL=start=172.18.161.250,end=172.18.161.254
    PUBLIC_NETWORK_GATEWAY="172.18.161.1"
    PUBLIC_INTERFACE=eth0

    Q_USE_PROVIDERNET_FOR_PUBLIC=True

    # Linuxbridge Settings
    Q_AGENT=linuxbridge
    LB_PHYSICAL_INTERFACE=eth0
    PUBLIC_PHYSICAL_NETWORK=default
    LB_INTERFACE_MAPPINGS=default:eth0

Using MacVTap instead of Open vSwitch
------------------------------------------

Security groups are not supported by the MacVTap agent. Due to that, devstack
configures the NoopFirewall driver on the compute node.

MacVTap agent does not support l3, dhcp and metadata agent. Due to that you can
chose between the following deployment scenarios:

Single node with provider networks using config drive and external l3, dhcp
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This scenario applies, if l3 and dhcp services are provided externally, or if
you do not require them.


::

    [[local|localrc]]
    HOST_IP=10.0.0.2
    SERVICE_HOST=10.0.0.2
    MYSQL_HOST=10.0.0.2
    RABBIT_HOST=10.0.0.2
    ADMIN_PASSWORD=secret
    MYSQL_PASSWORD=secret
    RABBIT_PASSWORD=secret
    SERVICE_PASSWORD=secret

    Q_ML2_PLUGIN_MECHANISM_DRIVERS=macvtap
    Q_USE_PROVIDER_NETWORKING=True

    enable_plugin neutron https://opendev.org/openstack/neutron

    ## MacVTap agent options
    Q_AGENT=macvtap
    PHYSICAL_NETWORK=default

    IPV4_ADDRS_SAFE_TO_USE="203.0.113.0/24"
    NETWORK_GATEWAY=203.0.113.1
    PROVIDER_SUBNET_NAME="provider_net"
    PROVIDER_NETWORK_TYPE="vlan"
    SEGMENTATION_ID=2010
    USE_SUBNETPOOL=False

    [[post-config|/$Q_PLUGIN_CONF_FILE]]
    [macvtap]
    physical_interface_mappings = $PHYSICAL_NETWORK:eth1

    [[post-config|$NOVA_CONF]]
    force_config_drive = True


Multi node with MacVTap compute node
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This scenario applies, if you require OpenStack provided l3, dhcp or metadata
services. Those are hosted on a separate controller and network node, running
some other l2 agent technology (in this example Open vSwitch). This node needs
to be configured for VLAN tenant networks.

For OVS, a similar configuration like described in the
:ref:`OVS Provider Network <ovs-provider-network-controller>` section can be
used. Just add the following line to this local.conf, which also loads
the MacVTap mechanism driver:

::

    [[local|localrc]]
    ...
    Q_ML2_PLUGIN_MECHANISM_DRIVERS=openvswitch,linuxbridge,macvtap
    ...

For the MacVTap compute node, use this local.conf:

::

    HOST_IP=10.0.0.3
    SERVICE_HOST=10.0.0.2
    MYSQL_HOST=10.0.0.2
    RABBIT_HOST=10.0.0.2
    ADMIN_PASSWORD=secret
    MYSQL_PASSWORD=secret
    RABBIT_PASSWORD=secret
    SERVICE_PASSWORD=secret

    # Services that a compute node runs
    disable_all_services
    enable_plugin neutron https://opendev.org/openstack/neutron
    ENABLED_SERVICES+=n-cpu,q-agt

    ## MacVTap agent options
    Q_AGENT=macvtap
    PHYSICAL_NETWORK=default

    [[post-config|/$Q_PLUGIN_CONF_FILE]]
    [macvtap]
    physical_interface_mappings = $PHYSICAL_NETWORK:eth1