diff --git a/config.yaml b/config.yaml
index 1be533bc..a1cf640b 100644
--- a/config.yaml
+++ b/config.yaml
@@ -70,8 +70,10 @@ options:
     type: string
     default: "physnet1:1000:2000"
     description: |
-      Space-delimited list of Neutron network-provider & vlan-id-ranges using
-      the following format "<provider>:<start>:<end> ...".
+      Space-delimited list of <physical_network>:<vlan_min>:<vlan_max> or
+      <physical_network> specifying physical_network names usable for VLAN
+      provider and tenant networks, as well as ranges of VLAN tags on each
+      available for allocation to tenant networks.
   # Network configuration options
   # by default all access is over 'private-address'
   os-data-network: