The interface group ID. There are two parts for this id depicted as follows: 31 7 0 +++++++++++++++++++++++++++++++++++++++++ + entity index + group index + + ( bit 8..31 ) ( bit 0..7 ) + +++++++++++++++++++++++++++++++++++++++++ From bit0 to bit7 (one byte), it is interfaces group index. From bit8 to bit31 (three bytes), it is the physical index the same as the entPhysicalIndex specified in ENTITY-MIB. Note that only entPhysicalIndex values that represent physical boards (i.e., associated entPhysicalClass value is 'module(9)') are permitted to exist in this table.