As per RFC:
The Trap-PDU of type linkDown contains as the first element of its variable-bindings, the name and value of the ifIndex instance for the affected interface.
The older SNMP trap API had a limitation that it was not possible to specify the indices for objects, now a new API SNMP notification was added to overcome this limitation.
This has been corrected in CR# xos0062912Upgrade to the following versions are necessary.
EXOS 22.1.1 (Released)
EXOS 21.1.2 (Released)
EXOS 16.1.3-GA-Jul16 (Released)
EXOS 16.2.2 (Released)