How to use QSFP+ Optics on QSFP28 Port
This Infoghraphic discusses the feasibility of this solution and provides a foundational guidance of how to configure the 100G switches. For Most Switches, QSFP+ Can Be Used on QSFP28 Port The former has just 4 electrical lanes that can be used as a 4x10GbE, 4x25GbE, while the latter supports 40G (4x10G). So from all of this information, a QSFP28 module breaks out into either 4x25G or 4x10G lanes, which depends on the transceiver used. For Most Switches, QSFP+ Can Be Used on QSFP28 Port A 100G QSFP28 port can generally take either a QSFP+ or QSFP28 optics. If the QSFP28 optics supports 25G lanes, then it can operate 4x25G breakout, 2x50G breakout or 1x100G. In all Cases, QSFP28 Optics Cannot Be Used on QSFP+ Port SFP+ can’t auto-negotiate to support SFP module, similarly QSFP28 modules cannot be used on the QSFP port, either.
Both ends of the two modules have to match and form factor needs to match as well. Additionally, port speed needs to be equal or greater than the optic used.
Conclusion QSFP Transceiver module, optical transceiver, qsfp optical transceiver QSFP+ modules can be used on the QSFP28 ports, but QSFP28 transceivers cannot transmit 100Gbps on the QSFP+ port. When using the QSFP optics on the QSFP28 port, don’t forget to configure your switch.