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Taikun OCP Guide

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Open vSwitch: High availability using DVR

This architecture example augments the self-service deployment
example with the Distributed Virtual Router (DVR) high-availability
mechanism that provides connectivity between self-service and provider
networks on compute nodes rather than network nodes for specific
scenarios. For instances with a floating IPv4 address, routing between
self-service and provider networks resides completely on the compute
nodes to eliminate single point of failure and performance issues with
network nodes. Routing also resides completely on the compute nodes for
instances with a fixed or floating IPv4 address using self-service
networks on the same distributed virtual router. However, instances with
a fixed IP address still rely on the network node for routing and SNAT
services between self-service and provider networks.

Consider the following attributes of this high-availability mechanism
to determine practicality in your environment:

  • Only provides connectivity to an instance via the compute node on
    which the instance resides if the instance resides on a self-service
    network with a floating IPv4 address. Instances on self-service networks
    with only an IPv6 address or both IPv4 and IPv6 addresses rely on the
    network node for IPv6 connectivity.
  • The instance of a router on each compute node consumes an IPv4
    address on the provider network on which it contains a gateway.

Prerequisites

Modify the compute nodes with the following components:

  • Install the OpenStack Networking layer-3 agent.

Note

Consider adding at least one additional network node to provide
high-availability for instances with a fixed IP address. See See config-dvr-snat-ha-ovs for
more information.

Architecture

High-availability using Open vSwitch with DVR - overview

The following figure shows components and connectivity for one
self-service network and 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 with a port on the OVS integration
bridge.

High-availability using Open vSwitch with DVR - components and connectivity - one network

Example configuration

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

Controller node

  1. In the neutron.conf file:
    • Enable distributed routing by default for all routers.

      [DEFAULT]
      router_distributed = True

Note

For a large scale cloud, if your deployment is running DVR with DHCP,
we recommend you set host_dvr_for_dhcp=False to achieve
higher L3 agent router processing performance. When this is set to
False, DNS functionality will not be available via the DHCP namespace
(dnsmasq) however, a different nameserver will have to be configured,
for example, by specifying a value in dns_nameservers for
subnets.

  1. Restart the following services:
    • Server

Network node

  1. In the openvswitch_agent.ini file, enable
    distributed routing.

    [agent]
    enable_distributed_routing = True
  2. In the l3_agent.ini file, configure the layer-3
    agent to provide SNAT services.

    [DEFAULT]
    agent_mode = dvr_snat

Note

agent_mode = dvr_snat is not supported on compute nodes.
For discussion please see: bug
#1934666

  1. Restart the following services:
    • Open vSwitch agent
    • Layer-3 agent

Compute nodes

  1. Install the Networking service layer-3 agent.

  2. In the openswitch_agent.ini file, enable distributed
    routing.

    [agent]
    enable_distributed_routing = True
  3. In the l3_agent.ini file, configure the layer-3
    agent.

    [DEFAULT]
    interface_driver = openvswitch
    agent_mode = dvr
  4. Restart the following services:

    • Open vSwitch agent
    • Layer-3 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                    |
    +--------------------------------------+--------------------+----------+-------------------+-------+-------+---------------------------+
    | 05d980f2-a4fc-4815-91e7-a7f7e118c0db | L3 agent           | compute1 | nova              | True  | UP    | neutron-l3-agent          |
    | 1236bbcb-e0ba-48a9-80fc-81202ca4fa51 | Metadata agent     | compute2 | None              | True  | UP    | neutron-metadata-agent    |
    | 2a2e9a90-51b8-4163-a7d6-3e199ba2374b | L3 agent           | compute2 | nova              | True  | UP    | neutron-l3-agent          |
    | 457d6898-b373-4bb3-b41f-59345dcfb5c5 | Open vSwitch agent | compute2 | None              | True  | UP    | neutron-openvswitch-agent |
    | 513caa68-0391-4e53-a530-082e2c23e819 | Linux bridge agent | compute1 | None              | True  | UP    | neutron-linuxbridge-agent |
    | 71f15e84-bc47-4c2a-b9fb-317840b2d753 | DHCP agent         | compute2 | nova              | True  | UP    | neutron-dhcp-agent        |
    | 8805b962-de95-4e40-bdc2-7a0add7521e8 | L3 agent           | network1 | nova              | True  | UP    | neutron-l3-agent          |
    | a33cac5a-0266-48f6-9cac-4cef4f8b0358 | Open vSwitch agent | network1 | None              | True  | UP    | neutron-openvswitch-agent |
    | a6c69690-e7f7-4e56-9831-1282753e5007 | Metadata agent     | compute1 | None              | True  | UP    | neutron-metadata-agent    |
    | af11f22f-a9f4-404f-9fd8-cd7ad55c0f68 | DHCP agent         | compute1 | nova              | True  | UP    | neutron-dhcp-agent        |
    | bcfc977b-ec0e-4ba9-be62-9489b4b0e6f1 | Open vSwitch agent | compute1 | None              | True  | UP    | neutron-openvswitch-agent |
    +--------------------------------------+--------------------+----------+-------------------+-------+-------+---------------------------+

Create initial networks

Similar to the self-service deployment example, this configuration
supports multiple VXLAN self-service networks. After enabling
high-availability, all additional routers use distributed routing. The
following procedure creates an additional self-service network and
router. The Networking service also supports adding distributed routing
to existing routers.

  1. Source a regular (non-administrative) project
    credentials.

  2. Create a self-service network.

    $ openstack network create selfservice2
    +-------------------------+--------------+
    | Field                   | Value        |
    +-------------------------+--------------+
    | admin_state_up          | UP           |
    | mtu                     | 1450         |
    | name                    | selfservice2 |
    | port_security_enabled   | True         |
    | revision_number         | 1            |
    | router:external         | Internal     |
    | shared                  | False        |
    | status                  | ACTIVE       |
    | tags                    | []           |
    +-------------------------+--------------+
  3. Create a IPv4 subnet on the self-service network.

    $ openstack subnet create --subnet-range 192.0.2.0/24 \
      --network selfservice2 --dns-nameserver 8.8.4.4 selfservice2-v4
    +-------------------+---------------------------+
    | Field             | Value                     |
    +-------------------+---------------------------+
    | allocation_pools  | 192.0.2.2-192.0.2.254     |
    | cidr              | 192.0.2.0/24              |
    | dns_nameservers   | 8.8.4.4                   |
    | enable_dhcp       | True                      |
    | gateway_ip        | 192.0.2.1                 |
    | ip_version        | 4                         |
    | name              | selfservice2-v4           |
    | revision_number   | 1                         |
    | tags              | []                        |
    +-------------------+---------------------------+
  4. Create a IPv6 subnet on the self-service network.

    $ openstack subnet create --subnet-range fd00:192:0:2::/64 --ip-version 6 \
      --ipv6-ra-mode slaac --ipv6-address-mode slaac --network selfservice2 \
      --dns-nameserver 2001:4860:4860::8844 selfservice2-v6
    +-------------------+------------------------------------------------------+
    | Field             | Value                                                |
    +-------------------+------------------------------------------------------+
    | allocation_pools  | fd00:192:0:2::2-fd00:192:0:2:ffff:ffff:ffff:ffff     |
    | cidr              | fd00:192:0:2::/64                                    |
    | dns_nameservers   | 2001:4860:4860::8844                                 |
    | enable_dhcp       | True                                                 |
    | gateway_ip        | fd00:192:0:2::1                                      |
    | ip_version        | 6                                                    |
    | ipv6_address_mode | slaac                                                |
    | ipv6_ra_mode      | slaac                                                |
    | name              | selfservice2-v6                                      |
    | revision_number   | 1                                                    |
    | tags              | []                                                   |
    +-------------------+------------------------------------------------------+
  5. Create a router.

    $ openstack router create router2
    +-----------------------+---------+
    | Field                 | Value   |
    +-----------------------+---------+
    | admin_state_up        | UP      |
    | name                  | router2 |
    | revision_number       | 1       |
    | status                | ACTIVE  |
    | tags                  | []      |
    +-----------------------+---------+
  6. Add the IPv4 and IPv6 subnets as interfaces on the router.

    $ openstack router add subnet router2 selfservice2-v4
    $ openstack router add subnet router2 selfservice2-v6

    Note

    These commands provide no output.

  7. Add the provider network as a gateway on the router.

    $ openstack router set router2 --external-gateway provider1

Verify network operation

  1. Source the administrative project credentials.

  2. Verify distributed routing on the router.

    $ openstack router show router2
    +-------------------------+---------+
    | Field                   | Value   |
    +-------------------------+---------+
    | admin_state_up          | UP      |
    | distributed             | True    |
    | ha                      | False   |
    | name                    | router2 |
    | revision_number         | 1       |
    | status                  | ACTIVE  |
    +-------------------------+---------+
  3. On each compute node, verify creation of a qrouter
    namespace with the same ID.

    Compute node 1:

    # ip netns
    qrouter-78d2f628-137c-4f26-a257-25fc20f203c1

    Compute node 2:

    # ip netns
    qrouter-78d2f628-137c-4f26-a257-25fc20f203c1
  4. On the network node, verify creation of the snat and
    qrouter namespaces with the same ID.

    # ip netns
    snat-78d2f628-137c-4f26-a257-25fc20f203c1
    qrouter-78d2f628-137c-4f26-a257-25fc20f203c1

    Note

    The namespace for router 1 from deploy-ovs-selfservice should also appear on network
    node 1 because of creation prior to enabling distributed routing.

  5. Launch an instance with an interface on the additional
    self-service network. For example, a CirrOS image using flavor ID 1.

    $ openstack server create --flavor 1 --image cirros --nic net-id=NETWORK_ID selfservice-instance2

    Replace NETWORK_ID with the ID of the additional
    self-service network.

  6. Determine the IPv4 and IPv6 addresses of the instance.

    $ openstack server list
    +--------------------------------------+-----------------------+--------+----------------------------------------------------------+--------+---------+
    | ID                                   | Name                  | Status | Networks                                                 | Image  | Flavor  |
    +--------------------------------------+-----------------------+--------+----------------------------------------------------------+--------+---------+
    | bde64b00-77ae-41b9-b19a-cd8e378d9f8b | selfservice-instance2 | ACTIVE | selfservice2=fd00:192:0:2:f816:3eff:fe71:e93e, 192.0.2.4 | cirros | m1.tiny |
    +--------------------------------------+-----------------------+--------+----------------------------------------------------------+--------+---------+
  7. Create a floating IPv4 address on the provider network.

    $ openstack floating ip create provider1
    +-------------------+--------------------------------------+
    | Field             | Value                                |
    +-------------------+--------------------------------------+
    | fixed_ip          | None                                 |
    | id                | 0174056a-fa56-4403-b1ea-b5151a31191f |
    | instance_id       | None                                 |
    | ip                | 203.0.113.17                         |
    | pool              | provider1                            |
    | revision_number   | 1                                    |
    | tags              | []                                   |
    +-------------------+--------------------------------------+
  8. Associate the floating IPv4 address with the instance.

    $ openstack server add floating ip selfservice-instance2 203.0.113.17

    Note

    This command provides no output.

  9. On the compute node containing the instance, verify creation of
    the fip namespace with the same ID as the provider
    network.

    # ip netns
    fip-4bfa3075-b4b2-4f7d-b88e-df1113942d43

Network traffic flow

This section only contains flow scenarios that benefit from
distributed virtual routing or that differ from conventional operation.
For other flow scenarios, see deploy-ovs-selfservice-networktrafficflow.

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

Similar to deploy-ovs-selfservice-networktrafficflow-ns1, except
the router namespace on the network node becomes the SNAT namespace. The
network node still contains the router namespace, but it serves no
purpose in this case.

High-availability using Open vSwitch with DVR - network traffic flow - north/south scenario 1

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

For instances with a floating IPv4 address using a self-service
network on a distributed router, the compute node containing the
instance 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. north-south traffic passing between the
instance and external networks such as the Internet.

  • Instance 1 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 compute node:

  1. The physical network infrastructure (1) forwards the packet to the
    provider physical network interface (2).
  2. The provider physical network interface forwards the packet to the
    OVS provider bridge provider network port (3).
  3. The OVS provider bridge swaps actual VLAN tag 101 with the internal
    VLAN tag.
  4. The OVS provider bridge phy-br-provider port (4)
    forwards the packet to the OVS integration bridge
    int-br-provider port (5).
  5. The OVS integration bridge port for the provider network (6) removes
    the internal VLAN tag and forwards the packet to the provider network
    interface (7) in the floating IP namespace. This interface responds to
    any ARP requests for the instance floating IPv4 address.
  6. The floating IP namespace routes the packet (8) to the distributed
    router namespace (9) using a pair of IP addresses on the DVR internal
    network. This namespace contains the instance floating IPv4
    address.
  7. The router performs DNAT on the packet which changes the destination
    IP address to the instance IP address on the self-service network via
    the self-service network interface (10).
  8. The router forwards the packet to the OVS integration bridge port
    for the self-service network (11).
  9. The OVS integration bridge adds an internal VLAN tag to the
    packet.
  10. The OVS integration bridge removes the internal VLAN tag from the
    packet.
  11. The OVS integration bridge security group port (12) forwards the
    packet to the security group bridge OVS port (13) via veth
    pair.
  12. Security group rules (14) on the security group bridge handle
    firewalling and connection tracking for the packet.
  13. The security group bridge instance port (15) forwards the packet to
    the instance interface (16) via veth pair.

High-availability using Open vSwitch with DVR - network traffic flow - north/south scenario 2

Note

Egress traffic follows similar steps in reverse, except SNAT changes
the source IPv4 address of the packet to the floating IPv4 address.

East-west
scenario 1: Instances on different networks on the same router

Instances with fixed IPv4/IPv6 address or floating IPv4 address on
the same compute node communicate via router on the compute node.
Instances on different compute nodes communicate via an instance of the
router on each compute node.

Note

This scenario places the instances on different compute nodes to show
the most complex situation.

The following steps involve compute node 1:

  1. The instance interface (1) forwards the packet to the security
    group bridge instance port (2) via veth pair.

  2. Security group rules (3) on the security group bridge handle
    firewalling and connection tracking for the packet.

  3. The security group bridge OVS port (4) forwards the packet to the
    OVS integration bridge security group port (5) via veth
    pair.

  4. The OVS integration bridge adds an internal VLAN tag to the
    packet.

  5. The OVS integration bridge port for self-service network 1 (6)
    removes the internal VLAN tag and forwards the packet to the
    self-service network 1 interface in the distributed router namespace
    (6).

  6. The distributed router namespace routes the packet to
    self-service network 2.

  7. The self-service network 2 interface in the distributed router
    namespace

    (8) forwards the packet to the OVS integration bridge port for
    self-service network 2 (9).

  8. The OVS integration bridge adds an internal VLAN tag to the
    packet.

  9. The OVS integration bridge exchanges the internal VLAN tag for an
    internal tunnel ID.

  10. The OVS integration bridge patch-tun port (10)
    forwards the packet to the OVS tunnel bridge patch-int port
    (11).

  11. The OVS tunnel bridge (12) wraps the packet using VNI
    101.

  12. The underlying physical interface (13) for overlay networks
    forwards the packet to compute node 2 via the overlay network
    (14).

The following steps involve compute node 2:

  1. The underlying physical interface (15) for overlay networks forwards
    the packet to the OVS tunnel bridge (16).
  2. The OVS tunnel bridge unwraps the packet and adds an internal tunnel
    ID to it.
  3. The OVS tunnel bridge exchanges the internal tunnel ID for an
    internal VLAN tag.
  4. The OVS tunnel bridge patch-int patch port (17)
    forwards the packet to the OVS integration bridge patch-tun
    patch port (18).
  5. The OVS integration bridge removes the internal VLAN tag from the
    packet.
  6. The OVS integration bridge security group port (19) forwards the
    packet to the security group bridge OVS port (20) via veth
    pair.
  7. Security group rules (21) on the security group bridge handle
    firewalling and connection tracking for the packet.
  8. The security group bridge instance port (22) forwards the packet to
    the instance 2 interface (23) via veth pair.

Note

Routing between self-service networks occurs on the compute node
containing the instance sending the packet. In this scenario, routing
occurs on compute node 1 for packets from instance 1 to instance 2 and
on compute node 2 for packets from instance 2 to instance 1.

High-availability using Open vSwitch with DVR - network traffic flow - east/west scenario 2

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