10G SFP+ and 25G SFP28 Compatibility Analysis

With 10G and 25G Ethernet equipment coexisting on the market today, we may frequently encounter the compatibility issues related to SFP+ and SFP28 form factors. Anyway, the newer 25GbE technologies are backward compatible with 10GbE, allowing customers to build and cross-connect a heterogeneous-speed Ethernet network. Here we list the frequently asked questions coming through average customers.

1.What is the difference between SFP28 and SFP+?

The pinouts of SFP28 and SFP+ connectors are mating compatible. However, SFP+ is designed to operate at speed up to 10 Gb/s whereas SFP28 can handle 25Gbps, 10Gbps and even 1Gbps. SFP28 has increased bandwidth, superior impedance control and less crosstalk than the SFP+ solution. Besides, the SFP28 copper cable has significantly greater bandwidth and lower loss compared to the SFP+ version.

2.Can the SFP28 be used in SFP+ slot, and what speed will I get?

Theoretically, plugging an SFP28 transceiver or cable into the 10G interface is feasible for certain devices to get 10Gb/s data rate, but this solution is not recommended, because it would be limited by the NIC and switch port that you have. Only when your SFP28 module is 100% compatible with your server or switch can you ensure that the links can go seamlessly and efficiently.

3.Can the SFP+ be used in SFP28 slot, and what speed will I get?

Theoretically, plugging an SFP+ transceiver or cable into the 25G SFP28 slot is feasible. But you also need to make sure ensure that your existing modules will be compatible with your switch gear. That is to say, although a switch that accepts the SFP28 form factor can physically accept a SFP+ connector in the same port, it doesn’t mean that your SFP+ modules will work on your equipment.

When shopping for new 25G leaf switches, if you have SFP+ modules you want to use, look for switches that accept the SFP28 form factor, which is physically capable of taking existing SFP+ modules. The same holds true for QSFP+ modules and QSFP28 ports. Carefully read the product specs to ensure that your existing modules will work with your new equipment.

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