Cause
A linkDown trap indicates that the entity sending the protocol (SNMPv2) recognizes a failure in one of the communication links represented in the agent configuration. The data passed within the event is:
The name and value of the ifIndex instance for the affected interface.
The name of the interface can be retrieved via an snmpget of .1.3.6.1.2.1.2.2.1.2.INST, where INST is the instance returned with the trap. The state is indicated by the included value of ifOperStatus.