This is intended to hold the name of a filter applied to traps forwarded to this destination, but the MIB's own description marks it as undefined and not yet specified at the time this MIB was written. Because its behavior was never finalized in this MIB, an admin should not rely on it to actually filter which trap types get forwarded to a given destination without confirming the specific device's implementation supports it. As an illustrative example only, if a later implementation did use this field, an admin might have set it to a filter name like "criticalOnly" to restrict a destination to only critical-severity traps, but this is not confirmed by the source description.