Aspects include receiving, at an input/output (I/O) processor, a transport control word (TCW) that includes an instruction to perform physical port mirroring. It is identified, by the I/O processor, a first port to be mirrored and a second port to perform the mirroring. The second port is a physical port on a host bus adapter (HBA). In response to outbound data being sent to the first port for transmission to a first target device and to the instruction specifying outbound port mirroring, the I/O processor sends a copy of the outbound data to a second target device via the second port. In response to receiving inbound data at the first port and to the instruction specifying inbound port mirroring, a copy of the inbound data is transmitted to the second target device via the second port.