Linux bridge: Self-service networks

This architecture example augments deploy-lb-provider to support a nearly limitless
quantity of entirely virtual networks. Although the Networking service
supports VLAN self-service networks, this example focuses on VXLAN
self-service networks. For more information on self-service networks,
see intro-os-networking-selfservice.

Prerequisites

Add one network node with the following components:

• Three network interfaces: management, provider, and overlay.

• OpenStack Networking Linux bridge layer-2 agent, layer-3 agent, and
  any

  dependencies.

Modify the compute nodes with the following components:

• Add one network interface: overlay.

Architecture

The following figure shows components and connectivity for one
self-service network and one untagged (flat) provider network. In this
particular case, the instance resides on the same compute node as the
DHCP agent for the network. If the DHCP agent resides on another compute
node, the latter only contains a DHCP namespace and Linux bridge with a
port on the overlay physical network interface.

Example configuration

Use the following example configuration as a template to add support
for self-service networks to an existing operational environment that
supports provider networks.

Controller node

1. In the neutron.conf file:

   • Enable routing and allow overlapping IP address ranges.

     [DEFAULT]
     service_plugins = router

2. In the ml2_conf.ini file:

   • Add vxlan to type drivers and project network
     types.

     [ml2]
     type_drivers = flat,vlan,vxlan
     tenant_network_types = vxlan

   • Enable the layer-2 population mechanism driver.

     [ml2]
     mechanism_drivers = linuxbridge,l2population

   • Configure the VXLAN network ID (VNI) range.

     [ml2_type_vxlan]
     vni_ranges = VNI_START:VNI_END

     Replace VNI_START and VNI_END with
     appropriate numerical values.

3. Restart the following services:
   • Server

Network node

1. Install the Networking service layer-3 agent.

2. In the neutron.conf file, configure common
   options:

3. In the linuxbridge_agent.ini file, configure the
   layer-2 agent.

   [linux_bridge]
   physical_interface_mappings = provider:PROVIDER_INTERFACE
   
   [vxlan]
   enable_vxlan = True
   l2_population = True
   local_ip = OVERLAY_INTERFACE_IP_ADDRESS
   
   [securitygroup]
   firewall_driver = iptables

   Warning

   By default, Linux uses UDP port 8472 for VXLAN tunnel
   traffic. This default value doesn’t follow the IANA standard, which
   assigned UDP port 4789 for VXLAN communication. As a
   consequence, if this node is part of a mixed deployment, where nodes
   with both OVS and Linux bridge must communicate over VXLAN tunnels, it
   is recommended that a line containing udp_dstport = 4789 be
   added to the [vxlan] section of all the Linux bridge agents. OVS follows
   the IANA standard.

   Replace PROVIDER_INTERFACE with the name of the
   underlying interface that handles provider networks. For example,
   eth1.

   Replace OVERLAY_INTERFACE_IP_ADDRESS with the IP address
   of the interface that handles VXLAN overlays for self-service
   networks.

4. In the l3_agent.ini file, configure the layer-3
   agent.

   [DEFAULT]
   interface_driver = linuxbridge

5. Start the following services:

   • Linux bridge agent
   • Layer-3 agent

Compute nodes

1. In the linuxbridge_agent.ini file, enable VXLAN
   support including layer-2 population.

   [vxlan]
   enable_vxlan = True
   l2_population = True
   local_ip = OVERLAY_INTERFACE_IP_ADDRESS

   Warning

   By default, Linux uses UDP port 8472 for VXLAN tunnel
   traffic. This default value doesn’t follow the IANA standard, which
   assigned UDP port 4789 for VXLAN communication. As a
   consequence, if this node is part of a mixed deployment, where nodes
   with both OVS and Linux bridge must communicate over VXLAN tunnels, it
   is recommended that a line containing udp_dstport = 4789 be
   added to the [vxlan] section of all the Linux bridge agents. OVS follows
   the IANA standard.

   Replace OVERLAY_INTERFACE_IP_ADDRESS with the IP address
   of the interface that handles VXLAN overlays for self-service
   networks.

2. Restart the following services:

   • Linux bridge agent

Verify service operation

1. Source the administrative project credentials.

2. Verify presence and operation of the agents.

   $ openstack network agent list
   +--------------------------------------+--------------------+----------+-------------------+-------+-------+---------------------------+
   | ID                                   | Agent Type         | Host     | Availability Zone | Alive | State | Binary                    |
   +--------------------------------------+--------------------+----------+-------------------+-------+-------+---------------------------+
   | 09de6af6-c5f1-4548-8b09-18801f068c57 | Linux bridge agent | compute2 | None              | True  | UP    | neutron-linuxbridge-agent |
   | 188945d1-9e70-4803-a276-df924e0788a4 | Linux bridge agent | compute1 | None              | True  | UP    | neutron-linuxbridge-agent |
   | e76c440d-d5f6-4316-a674-d689630b629e | DHCP agent         | compute1 | nova              | True  | UP    | neutron-dhcp-agent        |
   | e67367de-6657-11e6-86a4-931cd04404bb | DHCP agent         | compute2 | nova              | True  | UP    | neutron-dhcp-agent        |
   | e8174cae-6657-11e6-89f0-534ac6d0cb5c | Metadata agent     | compute1 | None              | True  | UP    | neutron-metadata-agent    |
   | ece49ec6-6657-11e6-bafb-c7560f19197d | Metadata agent     | compute2 | None              | True  | UP    | neutron-metadata-agent    |
   | 598f6357-4331-4da5-a420-0f5be000bec9 | L3 agent           | network1 | nova              | True  | UP    | neutron-l3-agent          |
   | f4734e0f-bcd5-4922-a19d-e31d56b0a7ae | Linux bridge agent | network1 | None              | True  | UP    | neutron-linuxbridge-agent |
   +--------------------------------------+--------------------+----------+-------------------+-------+-------+---------------------------+

Create initial networks

Verify network operation

Network traffic
flow

North-south
scenario 1: Instance with a fixed IP address

For instances with a fixed IPv4 address, the network node performs
SNAT on north-south traffic passing from self-service to external
networks such as the Internet. For instances with a fixed IPv6 address,
the network node performs conventional routing of traffic between
self-service and external networks.

• The instance resides on compute node 1 and uses self-service network
  1.
• The instance sends a packet to a host on the Internet.

The following steps involve compute node 1:

1. The instance interface (1) forwards the packet to the self-service
   bridge instance port (2) via veth pair.
2. Security group rules (3) on the self-service bridge handle
   firewalling and connection tracking for the packet.
3. The self-service bridge forwards the packet to the VXLAN interface
   (4) which wraps the packet using VNI 101.
4. The underlying physical interface (5) for the VXLAN interface
   forwards the packet to the network node via the overlay network
   (6).

The following steps involve the network node:

1. The underlying physical interface (7) for the VXLAN interface
   forwards the packet to the VXLAN interface (8) which unwraps the
   packet.
2. The self-service bridge router port (9) forwards the packet to the
   self-service network interface (10) in the router namespace.
   • For IPv4, the router performs SNAT on the packet which changes the
     source IP address to the router IP address on the provider network and
     sends it to the gateway IP address on the provider network via the
     gateway interface on the provider network (11).
   • For IPv6, the router sends the packet to the next-hop IP address,
     typically the gateway IP address on the provider network, via the
     provider gateway interface (11).
3. The router forwards the packet to the provider bridge router port
   (12).
4. The VLAN sub-interface port (13) on the provider bridge forwards the
   packet to the provider physical network interface (14).
5. The provider physical network interface (14) adds VLAN tag 101 to
   the packet and forwards it to the Internet via physical network
   infrastructure (15).

North-south
scenario 2: Instance with a floating IPv4 address

For instances with a floating IPv4 address, the network node performs
SNAT on north-south traffic passing from the instance to external
networks such as the Internet and DNAT on north-south traffic passing
from external networks to the instance. Floating IP addresses and NAT do
not apply to IPv6. Thus, the network node routes IPv6 traffic in this
scenario.

• The instance resides on compute node 1 and uses self-service network
  1.
• A host on the Internet sends a packet to the instance.

The following steps involve the network node:

1. The physical network infrastructure (1) forwards the packet to the
   provider physical network interface (2).
2. The provider physical network interface removes VLAN tag 101 and
   forwards the packet to the VLAN sub-interface on the provider
   bridge.
3. The provider bridge forwards the packet to the self-service router
   gateway port on the provider network (5).
   • For IPv4, the router performs DNAT on the packet which changes the
     destination IP address to the instance IP address on the self-service
     network and sends it to the gateway IP address on the self-service
     network via the self-service interface (6).
   • For IPv6, the router sends the packet to the next-hop IP address,
     typically the gateway IP address on the self-service network, via the
     self-service interface (6).
4. The router forwards the packet to the self-service bridge router
   port (7).
5. The self-service bridge forwards the packet to the VXLAN interface
   (8) which wraps the packet using VNI 101.
6. The underlying physical interface (9) for the VXLAN interface
   forwards the packet to the network node via the overlay network
   (10).

The following steps involve the compute node:

1. The underlying physical interface (11) for the VXLAN interface
   forwards the packet to the VXLAN interface (12) which unwraps the
   packet.
2. Security group rules (13) on the self-service bridge handle
   firewalling and connection tracking for the packet.
3. The self-service bridge instance port (14) forwards the packet to
   the instance interface (15) via veth pair.

East-west
scenario 1: Instances on the same network

Instances with a fixed IPv4/IPv6 or floating IPv4 address on the same
network communicate directly between compute nodes containing those
instances.

By default, the VXLAN protocol lacks knowledge of target location and
uses multicast to discover it. After discovery, it stores the location
in the local forwarding database. In large deployments, the discovery
process can generate a significant amount of network that all nodes must
process. To eliminate the latter and generally increase efficiency, the
Networking service includes the layer-2 population mechanism driver that
automatically populates the forwarding database for VXLAN interfaces.
The example configuration enables this driver. For more information, see
config-plugin-ml2.

• Instance 1 resides on compute node 1 and uses self-service network
  1.
• Instance 2 resides on compute node 2 and uses self-service network
  1.
• Instance 1 sends a packet to instance 2.

The following steps involve compute node 1:

1. The instance 1 interface (1) forwards the packet to the self-service
   bridge instance port (2) via veth pair.
2. Security group rules (3) on the self-service bridge handle
   firewalling and connection tracking for the packet.
3. The self-service bridge forwards the packet to the VXLAN interface
   (4) which wraps the packet using VNI 101.
4. The underlying physical interface (5) for the VXLAN interface
   forwards the packet to compute node 2 via the overlay network (6).

The following steps involve compute node 2:

1. The underlying physical interface (7) for the VXLAN interface
   forwards the packet to the VXLAN interface (8) which unwraps the
   packet.
2. Security group rules (9) on the self-service bridge handle
   firewalling and connection tracking for the packet.
3. The self-service bridge instance port (10) forwards the packet to
   the instance 1 interface (11) via veth pair.

East-west
scenario 2: Instances on different networks

Instances using a fixed IPv4/IPv6 address or floating IPv4 address
communicate via router on the network node. The self-service networks
must reside on the same router.

• Instance 1 resides on compute node 1 and uses self-service network
  1.
• Instance 2 resides on compute node 1 and uses self-service network
  2.
• Instance 1 sends a packet to instance 2.

The following steps involve the compute node:

1. The instance 1 interface (1) forwards the packet to the self-service
   bridge instance port (2) via veth pair.
2. Security group rules (3) on the self-service bridge handle
   firewalling and connection tracking for the packet.
3. The self-service bridge forwards the packet to the VXLAN interface
   (4) which wraps the packet using VNI 101.
4. The underlying physical interface (5) for the VXLAN interface
   forwards the packet to the network node via the overlay network
   (6).

The following steps involve the network node:

1. The underlying physical interface (7) for the VXLAN interface
   forwards the packet to the VXLAN interface (8) which unwraps the
   packet.
2. The self-service bridge router port (9) forwards the packet to the
   self-service network 1 interface (10) in the router namespace.
3. The router sends the packet to the next-hop IP address, typically
   the gateway IP address on self-service network 2, via the self-service
   network 2 interface (11).
4. The router forwards the packet to the self-service network 2 bridge
   router port (12).
5. The self-service network 2 bridge forwards the packet to the VXLAN
   interface (13) which wraps the packet using VNI 102.
6. The physical network interface (14) for the VXLAN interface sends
   the packet to the compute node via the overlay network (15).

The following steps involve the compute node:

1. The underlying physical interface (16) for the VXLAN interface sends
   the packet to the VXLAN interface (17) which unwraps the packet.
2. Security group rules (18) on the self-service bridge handle
   firewalling and connection tracking for the packet.
3. The self-service bridge instance port (19) forwards the packet to
   the instance 2 interface (20) via veth pair.