@@ -211,13 +211,15 @@ PHYSICAL_NETWORK=${PHYSICAL_NETWORK:-public}

 # Example: ``OVS_PHYSICAL_BRIDGE=br-eth1``

 OVS_PHYSICAL_BRIDGE=${OVS_PHYSICAL_BRIDGE:-br-ex}

+default_route_dev=$(ip route | grep ^default | awk '{print $5}')

+die_if_not_set $LINENO default_route_dev "Failure retrieving default route device"

 # With the linuxbridge agent, if using VLANs for tenant networks,

 # or if using flat or VLAN provider networks, set in ``localrc`` to

 # the name of the network interface to use for the physical

 # network.

 #

 # Example: ``LB_PHYSICAL_INTERFACE=eth1``

-LB_PHYSICAL_INTERFACE=${LB_PHYSICAL_INTERFACE:-}

+LB_PHYSICAL_INTERFACE=${LB_PHYSICAL_INTERFACE:-$default_route_dev}

 # When Neutron tunnels are enabled it is needed to specify the

 # IP address of the end point in the local server. This IP is set