The Maximum Receive Unit (MRU) this interface is permitted to receive.
At creation, if a value for this object is not specified, a default will
be chosen that is suitable for the type of lower interface on which this
interface is stacked.
This setting plus 2 bytes for HDLC address/control plus the length in
bytes of the HDLC CRC cannot exceed 65535. The maximum value for this
object reflects the largest possible value when no CRC is used;
technology constraints of a particular implementation may further limit
the upper bound value.