Description of ML2 VLAN configuration options

Configuration option = Default value	Description
[ml2_type_vlan]
network_vlan_ranges =	(ListOpt) 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.