use dhcp_release
diff --git a/stack.sh b/stack.sh
index 841cbb4..78851b9 100755
--- a/stack.sh
+++ b/stack.sh
@@ -826,6 +826,7 @@
 add_nova_flag "--rabbit_host=$RABBIT_HOST"
 add_nova_flag "--rabbit_password=$RABBIT_PASSWORD"
 add_nova_flag "--glance_api_servers=$GLANCE_HOSTPORT"
+add_nova_flag "--force_dhcp_release"
 if [ -n "$INSTANCES_PATH" ]; then
     add_nova_flag "--instances_path=$INSTANCES_PATH"
 fi