diff --git a/doc/source/dev/dev-quickstart.rst b/doc/source/dev/dev-quickstart.rst
index 57a63614b1..5762048692 100644
--- a/doc/source/dev/dev-quickstart.rst
+++ b/doc/source/dev/dev-quickstart.rst
@@ -147,7 +147,9 @@ access the internet through PUBLIC_INTERFACE::
 
     cat > /opt/stack/devstack/local.sh << END_LOCAL_SH
     #!/bin/sh
-    sudo iptables -t nat -A POSTROUTING -o br-ex -j MASQUERADE
+    ROUTE_TO_INTERNET=$(ip route get 8.8.8.8)
+    OBOUND_DEV=$(echo ${ROUTE_TO_INTERNET#*dev} | awk '{print $1}')
+    sudo iptables -t nat -A POSTROUTING -o $OBOUND_DEV -j MASQUERADE
     END_LOCAL_SH
     chmod 755 /opt/stack/devstack/local.sh