This 4-byte octet string captures the DXI2 header of the last SMDS PDU that triggered the 'Dxi2 Ae Invalid' violation, meaning the Address Extension (AE) bit or field in the DXI level-2 header was set incorrectly for the addressing mode this port uses. An admin decoding these 4 bytes can determine whether the CPE is using the wrong address-extension convention, which typically shows up when a device configured for one SMDS addressing format is connected to a port expecting another. For example, a CPE still configured for an older AE convention after a network-side addressing change would repeatedly generate this violation until it's reconfigured to match.