diff --git a/devstack/local.conf.node_1.sample b/devstack/local.conf.node_1.sample
index 4968b8ff..af76f35e 100644
--- a/devstack/local.conf.node_1.sample
+++ b/devstack/local.conf.node_1.sample
@@ -26,7 +26,7 @@ ADMIN_PASSWORD=password
 
 HOST_IP=10.250.201.24
 
-Q_ML2_PLUGIN_VLAN_TYPE_OPTIONS=(network_vlan_ranges=bridge:2001:3000)
+Q_ML2_PLUGIN_VLAN_TYPE_OPTIONS=(network_vlan_ranges=bridge:2001:3000,extern:3001:4000)
 OVS_BRIDGE_MAPPINGS=bridge:br-vlan
 
 # Specify Central Region name
diff --git a/devstack/plugin.sh b/devstack/plugin.sh
index ed8a0459..5378107c 100644
--- a/devstack/plugin.sh
+++ b/devstack/plugin.sh
@@ -84,10 +84,7 @@ function init_local_neutron_variables {
 
         local vlan_option="bridge:$TRICIRCLE_DEFAULT_VLAN_RANGE"
         local ext_option="extern:$TRICIRCLE_DEFAULT_EXT_RANGE"
-        local vlan_ranges=(network_vlan_ranges=$vlan_option)
-        if [ "$TRICIRCLE_START_SERVICES" == "False" ]; then
-            vlan_ranges=(network_vlan_ranges=$vlan_option,$ext_option)
-        fi
+        local vlan_ranges=(network_vlan_ranges=$vlan_option,$ext_option)
         Q_ML2_PLUGIN_VLAN_TYPE_OPTIONS=$vlan_ranges
 
         local vlan_mapping="bridge:$TRICIRCLE_DEFAULT_VLAN_BRIDGE"
diff --git a/doc/source/multi-pod-installation-devstack.rst b/doc/source/multi-pod-installation-devstack.rst
index 9b43082d..470dc4fa 100644
--- a/doc/source/multi-pod-installation-devstack.rst
+++ b/doc/source/multi-pod-installation-devstack.rst
@@ -104,13 +104,17 @@ RegionOne,
     (network_vlan_ranges=<physical network name>:<min vlan>:<max vlan>),
     you can change physical network name, but remember to adapt your change
     to the commands showed in this guide; also, change min VLAN and max vlan
-    to adapt the VLAN range your physical network supports::
+    to adapt the VLAN range your physical network supports. You need to
+    additionally specify the physical network "extern" to ensure the
+    central neutron can create "extern" physical network which located in
+    other pods::
 
-      Q_ML2_PLUGIN_VLAN_TYPE_OPTIONS=(network_vlan_ranges=bridge:2001:3000)
+      Q_ML2_PLUGIN_VLAN_TYPE_OPTIONS=(network_vlan_ranges=bridge:2001:3000,extern:3001:4000)
 
   - the format of OVS_BRIDGE_MAPPINGS is <physical network name>:<ovs bridge name>,
     you can change these names, but remember to adapt your change to the
-    commands showed in this guide::
+    commands showed in this guide. You do not need specify the bridge mapping
+    for "extern", because this physical network is located in other pods::
 
       OVS_BRIDGE_MAPPINGS=bridge:br-vlan