diff --git a/vagrant--devstack/provision/openstack.sh b/vagrant--devstack/provision/openstack.sh
index 098e360..321ef41 100755
--- a/vagrant--devstack/provision/openstack.sh
+++ b/vagrant--devstack/provision/openstack.sh
@@ -38,6 +38,8 @@ cd devstack || exit 1
 ##
 ## Create configuration
 ## 
+## Ref. https://docs.openstack.org/devstack/latest/guides/neutron.html
+## 
 cat > local.conf <<-MARK
 [[local|localrc]]