An integer identifier for the Ethernet subinterface, used in
conjunction with the command-line interface. It is provided here for
cross-reference purposes only.
The value must be unique among subinterfaces configured on the same
underlying Ethernet interface.
If this object is not configured, or is configured with a value of -1, a
nonzero value will be allocated internally and can be retrieved from
this object after table entry creation has succeeded.
A value of zero for this object is reserved for future use.