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Taikun OCP Guide

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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.

Note

The Linux bridge agent lacks support for other overlay protocols such
as GRE and Geneve.

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.

Note

You can keep the DHCP and metadata agents on each compute node or
move them to the network node.

Architecture

Self-service networks using Linux bridge - overview

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.

Self-service networks using Linux bridge - components and connectivity - one network

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).

Note

Return traffic follows similar steps in reverse. However, without a
floating IPv4 address, hosts on the provider or external networks cannot
originate connections to instances on the self-service network.

Self-service networks using Linux bridge - network traffic flow - north/south scenario 1

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.

Note

Egress instance traffic flows similar to north-south scenario 1,
except SNAT changes the source IP address of the packet to the floating
IPv4 address rather than the router IP address on the provider
network.

Self-service networks using Linux bridge - network traffic flow - north/south scenario 2

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.

Note

Return traffic follows similar steps in reverse.

Self-service networks using Linux bridge - network traffic flow - east/west scenario 1

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.

Note

Both instances reside on the same compute node to illustrate how
VXLAN enables multiple overlays to use the same layer-3 network.

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.

Note

Return traffic follows similar steps in reverse.

Self-service networks using Linux bridge - network traffic flow - east/west scenario 2

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