Description: There are two parts for the index depicted as follows:

31                15             0
+++++++++++++++++++++++++++++++++++
+ physical index  + cfgFile index +
+++++++++++++++++++++++++++++++++++

From bit0 to bit15 (two bytes) is the configuration file index; the
configuration file index is a monotonically increasing integer for
the sole purpose of indexing events. When it reaches the maximum
value, an extremely unlikely event, the agent wraps the value back
to 1 and may flush existing entries.

From bit16 to bit31 (two bytes) is the physical index the same
as the entPhysicalIndex specified in ENTITY-MIB(RFC2737).
If ENTITY-MIB is not supported, the value for this object is the unit ID for XRN
devices ,0 for non-XRN device which has only one slot,the board number for
non-XRN device which have several slots.

Any index beyond the above range will not be supported.