QSFP cables and ports are used to DDR (20 Gbps), QDR (40 Gbps), and FDR (56 Gbps) InfiniBand links.

QSFP Cable

The connector on a QSFP cable is long and narrow. The connector slides into the port.


QSFP port are recessed openings. The QSFP cable slides into the port.


CX4 cables are used for SDR (10 Gbps) and DDR (20 Gbps) speeds.

CX4 Cable

The connector on a CX4 cable is wider than the QSFP connector. The CX4 connector slides over the port on the card or switch.

CX4 Port

CX4 ports protrude from the switch or card. The CX4 connector slides over the port.

Hybrid Cables

Hybrid cables have a CX4 connector at one end and a QSFP cable at the other. These allow connections between newer QSFP cables and older CX4 switches or vice versa. Regardless of the cable type used, the connection will be at the speed of the slowest connected port. An FDR (56 Gbps) card using a hybrid cable that plugs in to a DDR (20 Gbps) switch will only run at the DDR speed, 20 Gbps.