Comment 7 for bug 1536768

Reviewed: https://review.openstack.org/329582
Committed: https://git.openstack.org/cgit/openstack/charm-neutron-openvswitch/commit/?id=85cf60219b3bdf92fca1bdfc19bb41b3dba0bd3a
Submitter: Jenkins
Branch: master

commit 85cf60219b3bdf92fca1bdfc19bb41b3dba0bd3a
Author: James Page <email address hidden>
Date: Tue Jun 14 18:09:52 2016 +0100

    Support new style (and multiple) external networks

    Note that this change only impacts use of this charm when
    Distributed Virtual Routing is enabled in a deployment.

    Switch the generated configuration to use "new" style external
    networks when ext-port is not set. In this case we configure:

      external_network_bridge = (intentionally blank)
      gateway_external_network_id = (blank)

    The current template configures external networks by using the default
    external_network_bridge=br-ex (implied when not set). This activates
    legacy code which assumes that a single external network exists on
    that bridge and the L3 Agent directly plugs itself in.
    provider:network_type, provider:physical_network and
    provider:segmentation_id are ignored. You cannot create multiple
    networks and you cannot use segmented networks (e.g. VLAN)

    By setting external_network_bridge = (intentionally blank) the L2
    Agent handles the configuration instead, this allows us to create
    multiple networks and also to use more complex network configurations
    such as VLAN. It is also possible to use the same physical connection
    with different segmentation IDs for both internal and external
    networks, as well as multiple external networks.

    Legacy/existing configurations where ext-port is set generate the same
    configuration as previous and should continue to work as before.
    Migration from legacy to new style configuration is not supported.

    Change-Id: I3d06581850ccbe5ea77741c4a546e663b2957a91
    Closes-Bug: #1536768