Each row represents information about the Layer-3 encapsulation header
of a particular mirror destination.
Rows in this table can be created or deleted via SNMP operations.
A row can only be created if the corresponding mirror destination
supports Layer-3 encapsulation; in the corresponding row in the
tMirrorDestinationTable, the value of
the object tMirrorDestinationEncapsulation must be equal to
'ether' or 'ipOnly'.