The use case is about collection of performance counters in the bridge related mibs. For example to associate BRIDGE-MIB::dot1dBasePortTable Informations to the right physical (defined by ifIndex) interface description.
As indicated in the mib, BRIDGE-MIB::dot1dBasePortTable is indexed by BRIDGE-MIB::dot1dBasePort which may (or not) map to ifIndex.
Mapping is done in the same table through BRIDGE-MIB::dot1dBasePortIfIndex whose value is the corresponding ifIndex
"The value of the instance of the ifIndex object,
defined in IF-MIB, for the interface corresponding
to this port."
With some of our switch we sometimes do not have a direct mapping between dot1dBasePort and ifIndex :
--extract of BRIDGE-MIB::dot1dBasePortTable for stacked HP switches
— dot1dBasePort is the same as ifIndex up to instance 52
BRIDGE-MIB::dot1dBasePortIfIndex.51 = INTEGER: 51
BRIDGE-MIB::dot1dBasePortIfIndex.52 = INTEGER: 52
— then (becaus of switch stacking ???) dot1dBasePort and ifIndex are no more equals
- dot1dBasePort 53 is associated to ifIndex 56 in the folowing line
BRIDGE-MIB::dot1dBasePortIfIndex.53 = INTEGER: 56
BRIDGE-MIB::dot1dBasePortIfIndex.54 = INTEGER: 57
BRIDGE-MIB::dot1dBasePortIfIndex.57 = INTEGER: 58