It seems this commit [1] caused regression for the external gateway use case again..
In ArpNotificationHandler you now check if the traffic is arriving from a neutron port (isNeutronPortConfigured).
However this causes an exception when using non-neutron interfaces, and the ARP isn't learned.

2016-11-13 12:29:00,303 | ERROR | pool-24-thread-1 | DOMNotificationRouterEvent | 167 - org.opendaylight.controller.sal-broker-impl - 1.5.0.SNAPSHOT | Delivery of notification org.opendaylight.controller.md.sal.binding.impl.LazySerializedDOMNotification@5fb4384a caused an error in listener org.opendaylight.controller.md.sal.binding.impl.BindingDOMNotificationListenerAdapter@68152c28
java.lang.IllegalArgumentException: Supplied value "154710820308539:eth1:flat" does not match required pattern "^[0-9a-fA-F]

-[0-9a-fA-F]

-[0-9a-fA-F]

-[0-9a-fA-F]

$"
at com.google.common.base.Preconditions.checkArgument(Preconditions.java:145)[65:com.google.guava:18.0.0]
at org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.yang.types.rev130715.Uuid.<init>(Uuid.java:55)[109:org.opendaylight.mdsal.model.ietf-yang-types-20130715:2013.7.15.10-SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.VpnUtil.isNeutronPortConfigured(VpnUtil.java:1201)[369:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.ArpNotificationHandler.onArpRequestReceived(ArpNotificationHandler.java:143)[369:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.yangtools.yang.binding.util.NotificationListenerInvoker.invokeNotification(NotificationListenerInvoker.java:91)[73:org.opendaylight.mdsal.yang-binding:0.10.0.SNAPSHOT]