Each Entry is created as a row in the
cl2natInterfaceConfigTable table when a user applies an
instance to an interface/vlan combination, and removed when
that instance is removed. A value of 0 in
cl2natInterfaceVlanIndex
indicates that this attachment is for untagged traffic. The
result of this lookup is actually an index that is used to
lookup the cl2natInstanceTable which gives the actual config
of the instance attached.