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10G SFP+ to 25G SFP28 or 10G SFP+ to 40G QSFP, which one to choose?

June 25, 2023

In recent years, with the increasing demand for bandwidth between servers and switches, the existing 10G networks have become saturated and upgrading to higher speed 10G networks is becoming necessary. Today’s data center network trend is 100G/200G/400G. So the question arises, which is the better transition solution to upgrade to 100G and beyond, 40G QSFP+ transceivers or 25G SFP28 transceivers. This article will provide the answer.

25G Ethernet vs. 40G Ethernet

 The 25G Ethernet standard is an incremental update of 10G with the smallest pluggable form factor known as SFP28, similar to SFP+. 25G SFP28 transceivers are backward compatible with SFP+ ports and existing data center infrastructure while seamlessly upgrading to 100G and higher rates. SFP28 features a single channel at 25G, supporting efficient upgrades to 100G server connectivity in 4x25G configurations. 25G Ethernet is commonly used for interconnects within data centers for storage, services, switches and 5G front-haul transmission.

Click here to view a guide on How to Choose a 25G SFP28 Transceiver.

Prior to the release of the 25G Ethernet standard, 40G Ethernet was the only upgrade transition path to higher speed 100G connectivity. QSFP+ is the dominant form factor for 40G Ethernet transceivers, providing four transmit channels and four receive channels to support 40G Ethernet applications. 40G Ethernet is primarily used for connectivity between data center switches, helping to break down connectivity bottlenecks between access switches and distribution switches.

10G SFP-40G QSFP-100G QSF28 vs 10G SFP-25G SFP28-100G QSFP28 Upgrade Path

10G-40G-100G vs. 10G-25G-100G Upgrade Path
Figure 1 – 10G-40G-100G vs. 10G-25G-100G Upgrade Path

1. 10G SFP+ to 40G QSFP+ to 100G QSFP28 upgrade path

The 10G-40G-100G upgrade path supports 4x10G parallel channels for 40G Ethernet and 10x10G parallel channels for 100G Ethernet. Based on a single channel of 10G, the upgrade path offers space efficiency and cost-effectiveness in cabling deployments. In addition, the underlying technology for 40G Ethernet only supports quad-channel transmission at 10G speeds, lacking advantages in terms of power consumption, server rack density, or compatibility with a wide range of speed transitions.

2. 10G SFP+ to 25G SFP28 to 100G QSFP28 upgrade path

The 10G-25G-100G upgrade path provides 2.5 times higher bandwidth connectivity than 10G in 25G Ethernet with only a slight increase in cost. The upgrade path enables the implementation of 100G Ethernet over 4x25G based on a 25G switch infrastructure without the need to replan or change server density per rack, thus saving significant fiber resources. Moreover, the power consumption of a 4x25Gbit/s configuration is much lower compared to a 10x10Gbit/s configuration.

Why choose 10G SFP+ to 25G SFP28 instead of 10G SFP+ to 40G QSFP

25G SFP28 Backward compatible with 10G SFP+

The 25G SFP28 has a similar form factor to the existing 10G SFP+, making it backward compatible with the 10G SFP+. In addition, 25G switches offer better compatibility than 40G switches. Most 25G switches and NICs (Network Interface Cards) support backward compatibility with 10G and provide greater flexibility to manage servers that gradually upgrade to higher data rates and match port speeds.

Higher 10G SFP+ bandwidth and dense 25G SFP28 port density

The 25G SFP28 transceiver enables network equipment manufacturers to provide 2.5 times the bandwidth connectivity of 10G at a similar power level, which is significant lower than 40G. In addition, the 25G SFP28 module allows for higher port density configurations than 40G QSFP modules.

 25G SFP28 better matches 50G/100G upgrade

25G Ethernet uses a single channel of 25G Serializer Deserializer (SerDes) technology, while 40G Ethernet consists of four 10G channels. This allows for the utilization of 25G SFP28 modules to establish a 50G Ethernet configurations with 2x25G and a 100G Ethernet configurations with 4x25G, without the need for replanning or altering the server density per rack, as shown in Figure 2.

25G SFP28 better suited for 50G and 100G upgrades
Figure 2 – 25G SFP28 better suited for 50G and 100G upgrades

25G-100G upgrade path is more cost effective than 40G-100G path

The 4x25G technology enables upgrades from 25G to 100G, resulting in cost savings in terms of CapEx (capital expenditure) and OpEx (operational expenditure) by utilizing existing cabling infrastructure and high backward compatibility. Overall, the 25G to 100G upgrade path significantly reduces the cost per gigabit by leveraging switch port capacity.


As cutting-edge technologies emerge and business demands grow, your 10G network infrastructure faces the challenge of upgrading to higher data rates. two solutions for transitioning to 100G Ethernet are 10G SFP+ to 25G SFP28 and 10G SFP+ to 40G QSFP+. The 25G SFP28 provides a future-proof approach to upgrading to 100G access while considering factors such as backward compatibility, power consumption, port density, adaptability to legacy 2x 25G and 4x 25 configurations, and cost effectiveness. As enterprise server access trends shift from 1G-10G to 10-25G, the shipment volume of 25G SFP28 ports is expected to continue growing in the coming years.