| SID | Description |
| 1 | A Link-Layer Frame contained an invalid CRC. |
| (Enable check_crc in the preprocessor config to get this alert.) | |
| 2 | A DNP3 Link-Layer Frame was dropped, due to an invalid length. |
| 3 | A Transport-Layer Segment was dropped during reassembly. |
| This happens when segments have invalid sequence numbers. | |
| 4 | The DNP3 Reassembly buffer was cleared before a complete fragment could |
| be reassembled. | |
| This happens when a segment carrying the "FIR" flag appears after some | |
| other segments have been queued. | |
| 5 | A DNP3 Link-Layer Frame is larger than 260 bytes. |
| 6 | A DNP3 Link-Layer Frame uses an address that is reserved. |
| 7 | A DNP3 request or response uses a reserved function code. |