How to Use 25G Switch for Switch-to-Server Connection
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How to Use 25G Switch for Switch-to-Server Connection

Posted on by FS.COM

As the demand for high bandwidth is soaring, 10GbE has met its bottleneck in switch-to-server connections. And 25G Ethernet is the new standard offering significant density, cost and power benefits for server to switch links. This makes 25G switch very popular in recent years. This post will discuss how to use 25G Ethernet switch with 100G uplinks to deploy switch-to-server links.

25G Switch port

Advantages of Using 25G Switch for Switch-to-Server Connection

25G Ethernet has broad market potential in the server interconnect applications. This part will explain the advantages of using 25G Ethernet switch for switch-to-server connections.

Faster Speed

Data center is expanding at an unprecedented pace now, driving the need for higher bandwidth between the servers and switches. This means 10GbE is no longer fast enough for switch-to-server connection. Therefore, several big data center and cloud computing providers (Google, Microsoft, Broadcom, Arista, Mellanox, etc.) have formed the 25 Gigabit Ethernet Consortium. In addition, IEEE also formed a 25G Ethernet study group.

Cost-Effective for Moving to 100G

Although the Ethernet speed upgrade path of data center is defined as 10G→40G→100G, the latest upgrade path for server connections will be 10G→25G→100G. This is because upgrading from 10GbE to 25GbE offers both CapEx and OpEx savings for backward compatibility. Further more, 25GbE provides a simpler path to future Ethernet speeds of 50 Gbps, 100 Gbps and beyond.

Commonly Used 25G Switches Comparison

Now, there are various 25G Ethernet switches from different suppliers in the market, the following table lists some 25GbE switches with 100G uplinks, and compare their features and prices:

Ports Switch Capability Switch Class Price (From Internet)
FS N8500-48B6C 48 25G SFP28 ports
6 100G QSFP28 ports
3.6Tbps ToR/Leaf Switch US$ 8799.00
Cisco Nexus 93180YC-FX 48 25G SFP28 ports
6 100G QSFP28 ports
3.6Tbps ToR/Leaf Switch ‎US$ 11681.99
Mellanox MSN2410-CB2FC 48 25G SFP28 ports
6 100G QSFP28 ports
4 Tbps ToR/Leaf Switch ‎US$ 16910.00
Edgecore AS7312-54XS 48 25G SFP28 ports
6 100G QSFP28 ports
1.8 Tbps ToR/Spine Switch Unknow

How to use 25G Switch to Build Switch-to-Server Connection

When use 25G Ethernet switch for switch-to-server connection, ToR switching architecture are often applied. And the 25G switch is deployed as ToR switch which supports 25GbE to servers with 100 GbE uplinks.

25g dac

Generally, SFP28 DAC cables are used as the low-cost copper server connections for 25G ToR switches. And the reach of these DAC cables is expected to be nearly the same as traditional passive DAC cables or about five meters.

For long reach switch-to-server connections, SFP28 transceivers are often used. It uses a 28Gbps lane specifically for TOR switch to server connectivity. Read this article for more details about 25G SFP28: Taking an In-depth Look at 25G SFP28.

SFP28 tansceiver

25GBASE-T transceiver is another alternative to 3-5m 25G copper cable for longer switch-to-server links. It provides a cost-effective solution for 25G ToR switch connecting to servers.

Conclusion

The storage space is really starting to need speed now, so 25G switch for switch-to-server connection will be inevitable in the future. Further more, 25 GbE also provides a more efficient use of hardware and a more logical upgrade path to 100G network.

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