Specifies the Vlan number for the layer-2 interfaces when
the object value of citneInterfaceTopNInterfaceType
for the same entry is 'layer2'. If the object value
of citneInterfaceTopNVlanNumber is other than zero and
the corresponding citneInterfaceTopNInterfaceType is
'layer2' for the same entry, then it indicates all
layer-2 interfaces in that VLAN is sampled. If the
object value of citneInterfaceTopNVlanNumber is zero
and the corresponding citneInterfaceTopNInterfaceType
is 'layer2' for the same entry, then it indicates all
layer-2 interfaces in the system regardless of their
Vlan number is sampled. If the object value of
citneInterfaceTopNInterfaceType is other than
'layer2', then citneInterfaceTopNVlanNumber has to take
the value of 0.
This object may not be modified if the associated
interfaceTopNRowStatus object is equal to 'active'.