Indicates the inner VLAN tag in a stacking VLAN.
If the VLAN is not of the stacking attribute or
you perform the query operation only by the outer VLAN,
this leaf must be set to -1.
Currently, ACL-based VLAN traffic statistics of only the
outer VLAN can be collected. Therefore, this value of
this leaf is not useful, and you'd better set the value to -1.
0 is not supported.