An in-band inspection device receives a packet and/or frame, and inspects the packet and/or frame "on the fly." The device can accept, reject, and/or modify the received packet and/or frame in accordance with the inspection. The device can operate in a fast mode wherein the received packet and/or frame can be transmitted as soon as, for example, a port address in the packet and/or frame is received, or in a slow mode wherein the received packet frame is buffered until, for example, at least the CRC of the packet and/or frame is beginning to be received.