This counts instances where a PDU's destination individual address was not found in the switch's address table, meaning the traffic is trying to reach an SMDS subscriber address that is not provisioned anywhere on this switch or known SMDS cloud segment. An admin treats a rising count as either a customer typo or misconfiguration in a destination address they are trying to reach, or a provisioning gap on the receiving end that has not been set up yet. For example, a customer reporting they cannot reach a new partner's SMDS address would have that failure reflected here if the partner's address genuinely is not provisioned in the switch's tables yet.