Comment 6 for bug 1536768

Reviewed: https://review.openstack.org/299205
Committed: https://git.openstack.org/cgit/openstack/charm-neutron-gateway/commit/?id=5dee017f12ad37838d5a3dfa784e60644edf4565
Submitter: Jenkins
Branch: master

commit 5dee017f12ad37838d5a3dfa784e60644edf4565
Author: Trent Lloyd <email address hidden>
Date: Wed Mar 23 00:33:06 2016 +0800

    Support new style (and multiple) external networks

    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) and update the README with
    information on using this new style of configuration.

    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. I do
    not believe it to be easy to migrate existing setups to the "new"
    style configuration automatically as changes to the neutron network
    configuration may be required (specifically: provider:physical_network
    will now be used when it was not before, and may not be correct) and
    the physical port needs to be moved from br-ex to br-data which the
    charm does not currently handle and is likely to error as it does not
    attempt removal first. Further work may be possible in this area.

    For information about this new style of configuration being preferred,
    see discussions in LP#1491668, LP#1525059 and
    http://docs.openstack.org/liberty/networking-guide/scenario-classic-ovs.html

    Change-Id: I8d2bb8098e080969e0445293b1ed79714b2c964f
    Related-Bug: #1491668
    Related-Bug: #1525059
    Closes-Bug: #1536768