How to Build 25G Network?

Driven by the boosting global data traffic, data center networks need better scalability, instant bandwidth provisioning, and application agility. Well, 25G is able to provide low-cost and high-efficiency for today’s network. Therefore, many suppliers provide various 25G devices such as 25G SFP28 for 25G network deployment. Well, how to build 25G network and what do you really need for its deployment? This post will offer you some clues.

Why Need 25G?

25G Ethernet, or 25 Gigabit Ethernet (25GbE), is developed by IEEE 802.3 Task Force P802.3by. The IEEE 802.3by standard uses technology defined for 100 Gigabit Ethernet implemented as four 25 Gbps lanes (IEEE 802.3bj). Actually, 40G and 100G have already existed before the emergence of 25G. However, 25G Ethernet can provide a more convenient path to Ethernet speeds of 50G, 100G and beyond. With 25G, network operators are no longer to use 40G Ethernet (using four lanes of 10G) to migrate to 100G,  but using 4 lanes of 25G. For more information about 25G network upgrade, read this article: 10G-25G-100G Network Upgrade: An Inevitable Roadmap for Future Data Centers.

What Do You Need for 25G Network Deployment?

To build a 25G network, several components are indispensable: 25G SFP28 transceiver, DAC/AOC cable, 25G adapter, and 25G Ethernet switch. Here will introduce a series of 25G products to guide your purchase.

25G Switch

The 25GbE switch is one of the most important 25G devices and the most popular type of 25GbE switch is the 25G 48-port switch. Nowadays, there is a variety of 25G switches from different suppliers in the market like Cisco, Juniper, and Mellanox. The following figure shows some 25GbE switches with 100G uplinks.

48-port 25GbE switches

Figure 1: 48-port 25GbE switches from FS, Cisco, Mellanox and Edgecore

25G Server Adapter

25G server adapter, also called 25G network interface card (NIC), is a printed circuit board that provides network communication capabilities. It is commonly used as a separate adapter card, which can be inserted into the server’s motherboard expansion slot. Usually, the NIC is built with an interface in the side plate. Some NICs such as FS NIC even have two or more network interface. As the 40G network card is costly and too large for the server, 25G NIC is definitely a proper one for today’s network.

25G Transceiver

SFP28 is designed for 25G signal transmission. It usually contains SFP-25G-SR, SFP-25G-LR and CWDM SFP28. The SFP-25G-SR is used for short distance transmission (up to 100m over MMF). While the SFP-25G-LR and CWDM SFP28 are applied for long distance transmission (up to 10 km over SMF). You can choose an appropriate one based on your need.

25G DAC/AOC Cables

For interconnections in Ethernet switches, applying 25G DAC/AOC cables may be a more suitable and cost-effective solution than using 25G transceivers. However, 25G DAC/AOC cables only for short transmission distance. 25G SFP28 DAC cables can transmit less than 5m, and 25G SFP28 AOC cables transmit up to 30m.

How to Build 25G Network?

After choosing the suitable 25G devices, here we can start to build 25G network.

When deploying 25G network, ToR/spine-leaf switching architecture is often applied. The spine-leaf architecture includes two layers – the spine layer and the leaf layer. The spine layer is the backbone of the network and the leaf layer interconnects with every spine switch. In this deployment, 25G switches are usually deployed as ToR/leaf switches in the leaf layer or the top of each cabinet. Through point-to-point cabling, these switches can connect directly to the 25G servers in all the cabinets. And you can use 25G DAC/AOC cables or 25G SR transceiver and fiber patch cables to connect the switch ports and 25G servers. In addition, you should insert a 25G NIC in each 25G server.

25g sfp28

Figure 2: 25G ToR/spine-leaf architecture deployment


This article presents some basic information about 25G Ethernet, how to build 25G network, and the devices needed for 25G network deployment like 25G SFP28 transceiver, DAC/AOC cable, 25G NIC, and 25G Ethernet switch. If you are considering to build 25 network, reliable suppliers like FS provide all the components mentioned above such as 25G SFP28. For more details, please visit

This entry was posted in Enterprise Network and tagged , , . Bookmark the permalink.