diff --git a/lib/neutron_plugins/ml2 b/lib/neutron_plugins/ml2
index 2ece210..7e80209 100644
--- a/lib/neutron_plugins/ml2
+++ b/lib/neutron_plugins/ml2
@@ -95,8 +95,16 @@
 
 
     # Allow for setup the flat type network
-    if [[ -z "$Q_ML2_PLUGIN_FLAT_TYPE_OPTIONS" && -n "$PHYSICAL_NETWORK" ]]; then
-            Q_ML2_PLUGIN_FLAT_TYPE_OPTIONS="flat_networks=$PHYSICAL_NETWORK"
+    if [[ -z "$Q_ML2_PLUGIN_FLAT_TYPE_OPTIONS" ]]; then
+        if [[ -n "$PHYSICAL_NETWORK" || -n "$PUBLIC_PHYSICAL_NETWORK" ]]; then
+            Q_ML2_PLUGIN_FLAT_TYPE_OPTIONS="flat_networks="
+            if [[ -n "$PHYSICAL_NETWORK" ]]; then
+                Q_ML2_PLUGIN_FLAT_TYPE_OPTIONS+="${PHYSICAL_NETWORK},"
+            fi
+            if [[ -n "$PUBLIC_PHYSICAL_NETWORK" ]]; then
+                Q_ML2_PLUGIN_FLAT_TYPE_OPTIONS+="${PUBLIC_PHYSICAL_NETWORK},"
+            fi
+        fi
     fi
     # REVISIT(rkukura): Setting firewall_driver here for
     # neutron.agent.securitygroups_rpc.is_firewall_enabled() which is