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Taikun OCP Guide

Table of Contents

Linux bridge: Provider networks

The provider networks architecture example provides layer-2
connectivity between instances and the physical network infrastructure
using VLAN (802.1q) tagging. It supports one untagged (flat) network and
up to 4095 tagged (VLAN) networks. The actual quantity of VLAN networks
depends on the physical network infrastructure. For more information on
provider networks, see intro-os-networking-provider.

Prerequisites

One controller node with the following components:

  • Two network interfaces: management and provider.
  • OpenStack Networking server service and ML2 plug-in.

Two compute nodes with the following components:

  • Two network interfaces: management and provider.
  • OpenStack Networking Linux bridge layer-2 agent, DHCP agent,
    metadata agent, and any dependencies.

Note

Larger deployments typically deploy the DHCP and metadata agents on a
subset of compute nodes to increase performance and redundancy. However,
too many agents can overwhelm the message bus. Also, to further simplify
any deployment, you can omit the metadata agent and use a configuration
drive to provide metadata to instances.

Architecture

Provider networks using Linux bridge - overview

The following figure shows components and connectivity for one
untagged (flat) 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 provider physical network
interface.

Provider networks using Linux bridge - components and connectivity - one network

The following figure describes virtual connectivity among components
for two tagged (VLAN) networks. Essentially, each network uses a
separate bridge that contains a port on the VLAN sub-interface on the
provider physical network interface. Similar to the single untagged
network case, the DHCP agent may reside on a different compute node.

Provider networks using Linux bridge - components and connectivity - multiple networks

Note

These figures omit the controller node because it does not handle
instance network traffic.

Example configuration

Use the following example configuration as a template to deploy
provider networks in your environment.

Controller node

  1. Install the Networking service components that provides the
    neutron-server service and ML2 plug-in.

  2. In the neutron.conf file:

    • Configure common options:

    • Disable service plug-ins because provider networks do not require
      any. However, this breaks portions of the dashboard that manage the
      Networking service. See the latest Install
      Tutorials and Guides
      for more information.

      [DEFAULT]
      service_plugins =
    • Enable two DHCP agents per network so both compute nodes can
      provide DHCP service provider networks.

      [DEFAULT]
      dhcp_agents_per_network = 2
    • If necessary, configure MTU <config-mtu>.

  3. In the ml2_conf.ini file:

    • Configure drivers and network types:

      [ml2]
      type_drivers = flat,vlan
      tenant_network_types =
      mechanism_drivers = linuxbridge
      extension_drivers = port_security
    • Configure network mappings:

      [ml2_type_flat]
      flat_networks = provider
      
      [ml2_type_vlan]
      network_vlan_ranges = provider

      Note

      The tenant_network_types option contains no value
      because the architecture does not support self-service networks.

      Note

      The provider value in the
      network_vlan_ranges option lacks VLAN ID ranges to support
      use of arbitrary VLAN IDs.

  4. Populate the database.

    # su -s /bin/sh -c "neutron-db-manage --config-file /etc/neutron/neutron.conf \
      --config-file /etc/neutron/plugins/ml2/ml2_conf.ini upgrade head" neutron
  5. Start the following services:

    • Server

Compute nodes

  1. Install the Networking service Linux bridge layer-2
    agent.

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

  3. In the linuxbridge_agent.ini file, configure the
    Linux bridge agent:

    [linux_bridge]
    physical_interface_mappings = provider:PROVIDER_INTERFACE
    
    [vxlan]
    enable_vxlan = False
    
    [securitygroup]
    firewall_driver = iptables

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

  4. In the dhcp_agent.ini file, configure the DHCP
    agent:

    [DEFAULT]
    interface_driver = linuxbridge
    enable_isolated_metadata = True
    force_metadata = True

    Note

    The force_metadata option forces the DHCP agent to
    provide a host route to the metadata service on
    169.254.169.254 regardless of whether the subnet contains
    an interface on a router, thus maintaining similar and predictable
    metadata behavior among subnets.

  5. In the metadata_agent.ini file, configure the
    metadata agent:

    [DEFAULT]
    nova_metadata_host = controller
    metadata_proxy_shared_secret = METADATA_SECRET

    The value of METADATA_SECRET must match the value of the
    same option in the [neutron] section of the
    nova.conf file.

  6. Start the following services:

    • Linux bridge agent
    • DHCP agent
    • Metadata 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    |
    +--------------------------------------+--------------------+----------+-------------------+-------+-------+---------------------------+

Create initial networks

Verify network operation

Network traffic flow

North-south
scenario: Instance with a fixed IP address

  • The instance resides on compute node 1 and uses provider 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 provider
    bridge instance port (2) via veth pair.
  2. Security group rules (3) on the provider bridge handle firewalling
    and connection tracking for the packet.
  3. The VLAN sub-interface port (4) on the provider bridge forwards the
    packet to the physical network interface (5).
  4. The physical network interface (5) adds VLAN tag 101 to the packet
    and forwards it to the physical network infrastructure switch (6).

The following steps involve the physical network infrastructure:

  1. The switch removes VLAN tag 101 from the packet and forwards it to
    the router (7).
  2. The router routes the packet from the provider network (8) to the
    external network (9) and forwards the packet to the switch (10).
  3. The switch forwards the packet to the external network (11).
  4. The external network (12) receives the packet.

Provider networks using Linux bridge - network traffic flow - north/south

Note

Return traffic follows similar steps in reverse.

East-west
scenario 1: Instances on the same network

Instances on the same network communicate directly between compute
nodes containing those instances.

  • Instance 1 resides on compute node 1 and uses provider network
    1.
  • Instance 2 resides on compute node 2 and uses provider 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 provider
    bridge instance port (2) via veth pair.
  2. Security group rules (3) on the provider bridge handle firewalling
    and connection tracking for the packet.
  3. The VLAN sub-interface port (4) on the provider bridge forwards the
    packet to the physical network interface (5).
  4. The physical network interface (5) adds VLAN tag 101 to the packet
    and forwards it to the physical network infrastructure switch (6).

The following steps involve the physical network infrastructure:

  1. The switch forwards the packet from compute node 1 to compute node 2
    (7).

The following steps involve compute node 2:

  1. The physical network interface (8) removes VLAN tag 101 from the
    packet and forwards it to the VLAN sub-interface port (9) on the
    provider bridge.
  2. Security group rules (10) on the provider bridge handle firewalling
    and connection tracking for the packet.
  3. The provider bridge instance port (11) forwards the packet to the
    instance 2 interface (12) via veth pair.

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

Note

Return traffic follows similar steps in reverse.

East-west
scenario 2: Instances on different networks

Instances communicate via router on the physical network
infrastructure.

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

Note

Both instances reside on the same compute node to illustrate how VLAN
tagging enables multiple logical layer-2 networks to use the same
physical layer-2 network.

The following steps involve the compute node:

  1. The instance 1 interface (1) forwards the packet to the provider
    bridge instance port (2) via veth pair.
  2. Security group rules (3) on the provider bridge handle firewalling
    and connection tracking for the packet.
  3. The VLAN sub-interface port (4) on the provider bridge forwards the
    packet to the physical network interface (5).
  4. The physical network interface (5) adds VLAN tag 101 to the packet
    and forwards it to the physical network infrastructure switch (6).

The following steps involve the physical network infrastructure:

  1. The switch removes VLAN tag 101 from the packet and forwards it to
    the router (7).
  2. The router routes the packet from provider network 1 (8) to provider
    network 2 (9).
  3. The router forwards the packet to the switch (10).
  4. The switch adds VLAN tag 102 to the packet and forwards it to
    compute node 1 (11).

The following steps involve the compute node:

  1. The physical network interface (12) removes VLAN tag 102 from the
    packet and forwards it to the VLAN sub-interface port (13) on the
    provider bridge.
  2. Security group rules (14) on the provider bridge handle firewalling
    and connection tracking for the packet.
  3. The provider bridge instance port (15) forwards the packet to the
    instance 2 interface (16) via veth pair.

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

Note

Return traffic follows similar steps in reverse.

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