A linkUp trap signifies that the SNMP entity, acting in an agent role, has detected that the ifOperStatus object for one of its communication links left the down state and transitioned into some other state (but not into the notPresent state). This other state is indicated by the included value of ifOperStatus.
1.3.6.1.6.3.1.1.5.4
Trap : linkUp
Objects : { ifIndex, ifAdminStatus, ifOperStatus }
OID : "1.3.6.1.6.3.1.1.5.4"
object : ifIndex type : INTEGER
object : ifAdminStatus type : INTEGER
object : ifOperStatus type : INTEGER