What 100GbE actually is

  • 100GbE is an Ethernet standard defined for data center interconnect, not a consumer extension of 10GbE
  • It was designed around the bandwidth of a server NIC rather than around client access
  • The practical result is a fabric where the network stops being the constraint on a storage or AI workload

How a 100GbE switch fits into a fabric

  • Leaf switches in the rack carry server traffic; spine switches interconnect the leaves
  • Two tiers is the normal shape for most data centers, and it keeps the failure domain small
  • The spine tier must have enough bandwidth that the core never becomes the ceiling

Port speeds, optics and the choices you actually make

  • QSFP28 cages serve 100GbE and can break out to 25GbE or 50GbE on compatible switches
  • DAC and AOC cables cover in-rack and adjacent-row runs; optics take over beyond about 5 metres
  • Buffer depth and the forwarding specification decide how a switch behaves under a burst

Choosing a 100GbE switch model

  • 32-port and 64-port platforms are the current mainstream, in 1U and 2U respectively
  • The SN2700, SN3700 and SN3800 families cover the entry, mainstream and core tiers
  • Match the model to the fabric role — edge, leaf or spine — rather than to port count alone


Related reading

What Is a 100GbE Switch?

A 100GbE (100 Gigabit Ethernet) switch is a datacenter network switch that provides 100 Gbps of bandwidth per port, enabling high-throughput, low-latency connectivity between servers, storage arrays, and compute nodes. 100GbE switches are built on specialized ASICs (such as NVIDIA Spectrum-1/Spectrum-2/Spectrum-3) that deliver cut-through latency under 300 nanoseconds and shared packet buffers of 12–64 MB for lossless RDMA transport.

In modern datacenter architectures, 100GbE switches serve as spine or leaf nodes in Clos topologies, connecting GPU clusters for AI training, NVMe-oF storage fabrics, and HPC interconnects where zero packet loss and sub-microsecond latency are non-negotiable.

100GbE Switch Specifications Comparison

Specification SN2700 SN3700 SN3800 SN4600
ASIC Spectrum-1 Spectrum-2 Spectrum-3 Spectrum-2
100G Ports 32 36 64 36
Throughput 6.4 Tbps 7.2 Tbps 12.8 Tbps 7.2 Tbps
Latency <300 ns <250 ns <250 ns <250 ns
Buffer 12 MB 16 MB 64 MB 16 MB
200G Support No 4 ports 36 ports No
RoCE v2 Yes Yes Yes Yes
OS MLNX-OS / Cumulus MLNX-OS / Cumulus / SONiC Cumulus / SONiC MLNX-OS / Cumulus / SONiC
Use Case HPC / Trading AI/ML / Storage Cloud Spine Edge / Outdoor

How to Choose a 100GbE Switch

  • HPC & financial trading → SN2700 (lowest cost, 32 ports, proven Spectrum-1)
  • AI/ML GPU clusters & NVMe-oF → SN3700 (36 ports, larger buffer, RoCE v2 optimized)
  • Cloud spine (200G/400G mixed) → SN3800 (64×100G / 36×200G, Spectrum-3)
  • Edge/outdoor/telecom → SN4600 (same ASIC as SN3700, -40°C to 55°C)

Frequently Asked Questions

What does 100GbE mean?

100GbE stands for 100 Gigabit Ethernet—a IEEE 802.3bj standard providing 100 Gbps of bandwidth per port using QSFP28 connectors. Each 100G port can be split into 2×50G or 4×25G using breakout cables.

Can 100GbE ports be split into slower speeds?

Yes. Each QSFP28 100GbE port supports fan-out: 1×100G, 2×50G, or 4×25G using breakout cables. A 36-port SN3700 can serve up to 144×25GbE connections.

What is RoCE v2 and why does it matter?

RoCE v2 (RDMA over Converged Ethernet) enables zero-CPU-copy data transfer over Ethernet with PFC (Priority Flow Control) and ECN (Explicit Congestion Notification) for lossless transport. It’s critical for GPU-to-GPU communication in AI training clusters.

Is a used 100GbE switch reliable?

Yes. Mellanox/NVIDIA switches have no moving parts (SSD storage, passive cooling fans), and used units are re-flashed, functionally tested, and port-verified before they ship. Mean time between failures exceeds 500,000 hours.

Shop 100GbE switches at Zhongxin Data — enterprise network hardware specialists. Worldwide shipping from Hong Kong, China.