Updated flat networking docs

The change updates and corrects a couple of issues with the
documenation on the flat network setup. This should help
clarify what is needed to get a combined vlan and flat
network topology running within OSA using neutron.

Change-Id: I1591609c917db19378aa1e3479c13f11d0c55085
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

doc/source/install-guide/configure-networking.rst

@@ -164,7 +164,7 @@ configure target host networking.
                container_bridge: "br-vlan"
                container_type: "veth"
                container_interface: "eth12"
-               host_bind_override: "eth12"
+               host_bind_override: "PHYSICAL_NETWORK_INTERFACE"
                type: "flat"
                net_name: "flat"
            - network:
@@ -182,6 +182,25 @@ configure target host networking.
    network. For example, 1:1000,2001:3000. Create a similar stanza for each
    additional network.
 
+   Replace ``PHYSICAL_NETWORK_INTERFACE`` with the network interface used for
+   flat networking. This **must** be a physical interface on the same L2 network
+   being used with the br-vlan devices. If no additional network interface is
+   available, a veth pair plugged into the br-vlan bridge can provide the needed
+   interface.
+
+   Example creating a veth-pair within an existing bridge
+
+   .. code-block:: text
+
+         # Create veth pair, don't bomb if already exists
+         pre-up ip link add br-vlan-veth type veth peer name PHYSICAL_NETWORK_INTERFACE || true
+         # Set both ends UP
+         pre-up ip link set br-vlan-veth up
+         pre-up ip link set PHYSICAL_NETWORK_INTERFACE up
+         # Delete veth pair on DOWN
+         post-down ip link del br-vlan-veth || true
+         bridge_ports br-vlan-veth
+
 .. note::
 
    Optionally, you can add one or more static routes to interfaces within

doc/source/install-guide/overview-hostnetworking.rst

@@ -85,19 +85,21 @@ Target hosts can contain the following network bridges:
 
    -  Mandatory.
 
-   -  Provides infrastructure for VLAN and flat networks.
+   -  Provides infrastructure for VLAN networks.
 
    -  Manually created and attaches to a physical or logical interface,
-      typically ``bond1``. Also attaches to ``eth11`` in each associated
+      typically ``bond1``. Attaches to ``eth11`` for vlan type networks
-      container. Does not contain an IP address because it only handles
+      in each associated container. It does not contain an IP address because
-      layer 2 connectivity.
+      it only handles layer 2 connectivity. This interface can support flat
+      networks as well, though additional bridge configuration will be needed.
+      See more on `network configuration here <configure-networking.html>`_
+
 
 `Figure 1.3, "Container network
 architecture" <overview-hostnetworking.html#fig_overview_networkarch-container>`_
 provides a visual representation of network components for services in
 containers.
 
- 
 
 **Figure 1.3. Container network architecture**