Procedure 7.18. Configuring the L3 Agent

1. Configuring Authentication

   1. Set the authentication strategy (auth_strategy) configuration key to keystone using the openstack-config command.

      # openstack-config --set /etc/neutron/metadata_agent.ini \
         DEFAULT auth_strategy keystone

   2. Set the authentication host (auth_host) configuration key to the IP address or host name of the Identity server.

      # openstack-config --set /etc/neutron/metadata_agent.ini \
         keystone_authtoken auth_host IP

      Replace IP with the IP address or host name of the Identity server.
   3. Set the administration tenant name (admin_tenant_name) configuration key to the name of the tenant that was created for the use of the networking services. Examples in this guide use services.

      # openstack-config --set /etc/neutron/metadata_agent.ini \
         keystone_authtoken admin_tenant_name services

   4. Set the administration user name (admin_user) configuration key to the name of the user that was created for the use of the networking services. Examples in this guide use neutron.

      # openstack-config --set /etc/neutron/metadata_agent.ini \
         keystone_authtoken admin_user neutron

   5. Set the administration password (admin_password) configuration key to the password that is associated with the user specified in the previous step.

      # openstack-config --set /etc/neutron/metadata_agent.ini \
         keystone_authtoken admin_password PASSWORD

      Note

      When used in admin_password, the $ and " " (space-bar) special characters must be properly escaped. Escape the $ in complex$password with a second $ to become complex$$password. Escape the " " (space-bar) char with quotation marks: complex password becomes "complex password".

2. Configuring the Interface Driver

   Set the value of the interface_driver configuration key in the /etc/neutron/l3_agent.ini file based on the networking plug-in being used. Execute only the configuration step that applies to the plug-in used in your environment.

   • Open vSwitch Interface Driver

     # openstack-config --set /etc/neutron/l3_agent.ini \
        DEFAULT interface_driver neutron.agent.linux.interface.OVSInterfaceDriver

   • Linux Bridge Interface Driver

     # openstack-config --set /etc/neutron/l3_agent.ini \
        DEFAULT interface_driver neutron.agent.linux.interface.BridgeInterfaceDriver

3. Configuring External Network Access

   The L3 agent connects to external networks using either an external bridge or an external provider network. When using the Open vSwitch plug-in either approach is supported. When using the Linux Bridge plug-in only the use of an external provider network is supported. Choose the approach that is most appropriate for the environment.

   • Using an External Bridge

     To use an external bridge you must create and configure it. Finally the OpenStack networking configuration must be updated to use it. This must be done on each system hosting an instance of the L3 agent.
     1. Use the ovs-ctl command to create the external bridge named br-ex.

        # ovs-vsctl add-br br-ex

     2. Ensure that the br-ex device persists on reboot by creating a /etc/sysconfig/network-scripts/ifcfg-br-ex file with these contents:

        DEVICE=br-ex
        DEVICETYPE=ovs
        TYPE=OVSBridge
        ONBOOT=yes
        BOOTPROTO=none

     3. Ensure that the value of the external_network_bridge configuration key in the /etc/neutron/l3_agent.ini file is br-ex. This ensures that the L3 agent will use the external bridge.

        # openstack-config --set /etc/neutron/l3_agent.ini \
           DEFAULT external_network_bridge br-ex

   • Using a Provider Network

     To connect the L3 agent to external networks using a provider network you must first have created the provider network. You must also have created a subnet and router to associate with it. The unique identifier of the router will be required to complete these steps.
     The value of the external_network_bridge configuration key in the /etc/neutron/l3_agent.ini file must be blank. This ensures that the L3 agent does not attempt to use an external bridge.

     # openstack-config --set /etc/neutron/l3_agent.ini \
        DEFAULT external_network_bridge ""

4. Starting the L3 Agent

   1. Use the service command to start the neutron-l3-agent service.

      # service neutron-l3-agent start

   2. Use the chkconfig command to ensure that the neutron-l3-agent service will be started automatically in the future.

      # chkconfig neutron-l3-agent on

5. Starting the Metadata Agent

   The OpenStack networking metadata agent allows virtual machine instances to communicate with the compute metadata service. It runs on the same hosts as the Layer 3 (L3) agent.
   1. Use the service command to start the neutron-metadata-agent service.

      # service neutron-metadata-agent start

   2. Use the chkconfig command to ensure that the neutron-metadata-agent service will be started automatically in the future.

      # chkconfig neutron-metadata-agent on

   The L3 agent has been configured and started.

6. Enable leastrouter scheduling

   The leastrouter scheduler enumerates L3 Agent router assignment, and consequently schedules the router to the L3 Agent with the fewest routers. This differs from the ChanceScheduler behaviour, which randomly selects from the candidate pool of L3 Agents. Enable the leastrouter scheduler by changing the router_scheduler_driver option in the neutron.conf file:

   router_scheduler_driver=neutron.scheduler.l3_agent_scheduler.LeastRoutersScheduler
   

   The router is scheduled once connected to a network. Unschedule the router using the neutron command:

   # neutron l3-agent-router-remove [l3 node] [router]

   Assign the router with using the neutron command:

   # neutron l3-agent-router-add [l3 node] [router]