Mellanox Spectrum-2 SN3420 Review: Powering Modern Data Centers with Flexibility & Performance

 

Data centers are racing toward faster 25G and 100G networks. But how do you upgrade affordably without wasting space or sacrificing performance? The answer lies in smart, high-density top-of-rack (ToR) switches. These devices sit at the top of server racks, acting as a central hub connecting all servers below to the rest of your network.

 

Meet NVIDIA’s Mellanox Spectrum-2 SN3420, a compact 1U switch built exactly for this job. It’s designed to help businesses smoothly transition from older 10G networks to modern 25G/100G infrastructures. With 48 ports for servers and 12 high-speed uplinks, it packs serious power into a slim 1-unit rack space.

 

So, what makes it special? Three things: performance handles heavy traffic—like AI data or cloud storage—at blistering speeds (2.4 Terabits per second) with near-zero delay. Not to mention its open networking capabilities. Unlike traditional switches that lock you into one vendor’s software, the SN3420 lets you choose your preferred operating system (like Cumulus Linux or SONiC). This means freedom, lower costs, and no more vendor traps. Its future-proof scalability lets you start with 10G today and then scale to 25G or 100G tomorrow. Its flexible design grows with your needs, protecting your investment.

 

Why should you care? If you manage a data center, cloud service, or storage-heavy applications (like AI or video processing), this switch delivers more speed per dollar while simplifying upgrades. Ready to future-proof your network without breaking the bank? Let’s explore how.

 

 

1. SN3420: Hardware and Key Specifications

 

The Mellanox Spectrum-2 SN3420 packs enterprise-grade hardware into a compact 1U chassis. Let’s break down what powers this workhorse.

 

Port Configuration
This switch offers 48 ports for connecting servers (10G/25G speeds) and 12 high-speed uplink ports (100G each). The uplinks use QSFP28 sockets, a common industry standard for high-density cabling. Crucially, these uplinks can be “split” using breakout cables. This means one 100G port can become four 25G ports or two 50G ports. Need more 25G connections instead of a few 100G links? The Mellanox Spectrum-2 SN3420 gives you that flexibility without extra hardware.

 

Performance Metrics
Don’t let the size fool you. The SN3420 moves data at a massive 2.4 Terabits per second (Tb/s). That’s like transferring over 300 full HD movies every second! It also processes 3.58 billion packets per second. Even better? It does this with incredibly low delay – just 425 nanoseconds. This “cut-through” latency means data flows almost instantly, critical for AI training or real-time analytics where every microsecond counts.

 

Robust Design
Built for the demanding data center, the Mellanox Spectrum-2 SN3420 fits neatly in a standard 1U rack space. Its power supplies (PSUs) and cooling fans are hot-swappable. If one fails, the backup (N+1 redundancy) kicks in instantly – no downtime. The advanced 42MB packet buffer is shared fairly among all ports. Think of it like traffic management: during sudden data surges, it prevents any single server connection from hogging bandwidth, ensuring smooth performance for everyone.

 

2. Standout Features

 

The Mellanox Spectrum-2 SN3420 isn’t just fast—it’s smart. Beyond raw hardware, NVIDIA packs it with features that simplify operations and unlock new possibilities.

 

Open Ethernet Ecosystem
The SN3420 eliminates vendor lock-in by supporting open network operating systems such as Cumulus Linux, SONiC, and bare-metal Linux (via ONIE). This hardware-software disaggregation physically decouples the switch from proprietary software, enabling you to select the optimal NOS for your specific requirements. The result is reduced costs and simplified integration with DevOps automation toolchains.

 

Advanced Telemetry & Visibility
Network issues cause significant downtime. NVIDIA’s What Just Happened (WJH) technology addresses this by providing real-time, detailed diagnostics. Functioning like a network “black box recorder,” WJH identifies the specific source, nature, and root cause of problems. Combined with hardware-accelerated telemetry and support for 512,000 flow counters, it delivers granular visibility into network performance. The outcome? Administrators can proactively identify and resolve bottlenecks before they impact users.

 

Performance and Scalability
Modern cloud infrastructures demand massive scalability. The Mellanox Spectrum-2 SN3420 delivers 512,000 shared entries for routing rules (ACLs), tunnels (VXLAN), and addresses—flexibly distributed as needed. It supports 10x more VXLAN tunnels than comparable switches, providing the capacity essential for large-scale virtualized multi-tenant cloud environments.

 

Cloud-Native Agility
Need custom networking? The programmable pipeline lets you parse or modify packets on the fly—no ASIC limitations. It also processes VXLAN encapsulation in a single step (single-pass routing), slashing latency. With support for 100,000+ NAT sessions, it’s built for dynamic cloud environments. As a result, teams can adapt faster, without compromises.

 

 

3. Ideal Use Cases

 

The SN3420 shines in real-world environments that demand speed, reliability, and flexibility. Here’s where it delivers maximum impact:

 

Data Center Modernization
For data centers migrating from 10G to 25G servers, the Mellanox Spectrum-2 SN3420 switch provides a high-density solution. Its 48 ports offer native 25GbE connectivity for an entire rack of contemporary servers. Additionally, the integrated 12x100GbE uplink ports enable seamless integration with spine switches or core networks. This design allows for server speed upgrades without requiring core network infrastructure replacement.

 

AI/ML and Storage Workloads
The NVIDIA Spectrum-2 SN3420 switch optimizes AI/ML training and high-performance storage workloads like NVMe-oF. Its support for RoCEv2 (RDMA over Converged Ethernet v2) combined with ultra-low latency (425ns) enables direct, efficient communication between GPUs and storage arrays. GPUDirect RDMA technology bypasses the CPU, delivering significantly higher performance for distributed AI training and low-latency storage access compared to traditional TCP/IP networks.

 

Hyperconverged Infrastructure (HCI)
The NVIDIA Spectrum-2 SN3420 switch is optimized for Hyperconverged Infrastructure (HCI) environments running VMware vSAN, Ceph, or similar storage. HCI’s high traffic demands are met by the switch’s 2.4 Tbps throughput, efficiently handling storage replication and VM data. A key feature is its large, shared packet buffer, which ensures lossless transport—eliminating packet drops critical for storage reliability and preventing performance degradation from head-of-line blocking.

 

Telecom and Edge Deployments
Building 5G radio networks or edge sites? While optimized for data centers, the Mellanox Spectrum-2 SN3420 inherits key features from NVIDIA’s telco-focused switches like the SN3750-SX. It supports Precision Time Protocol (PTP) for nanosecond clock synchronization and fits in space-constrained edge racks. Hot-swappable power and fans ensure uptime in remote locations.

 

4. Software Ecosystem and Manageability

 

The SN3420’s real power lies beyond hardware. Its open software tools simplify operations and future-proof your network.

 

NOS Flexibility
The NVIDIA SN3420 provides ultimate flexibility in network operating system (NOS) selection. Teams can deploy Cumulus Linux for its automation-friendly Linux tools, SONiC for cloud-scale orchestration, or standard bare-metal Linux via ONIE for full administrative control. This approach eliminates vendor lock-in, reduces operational costs, and ensures teams utilize the optimal NOS for their specific operational and architectural requirements.

 

NVIDIA Tools Integration
The SN3420 integrates with NVIDIA’s management ecosystem for enhanced network operations. NVIDIA NetQ provides real-time monitoring and proactive issue resolution for every device, port, and connection. This helps prevent downtime. NVIDIA AIR utilizes a virtual replica of the network infrastructure. This allows administrators to safely test upgrades, automation scripts, and configuration changes in a simulated environment prior to production deployment.

 

Container Support
The NVIDIA Spectrum-2-based SN3420 supports the execution of containerized applications directly on the switch hardware. This capability enables the secure deployment of custom tools such as monitoring agents, security applications, and analytics platforms. Strict resource isolation ensures these containers operate without impacting core switching performance or stability, providing enhanced visibility and workflow automation.

 

5. Competitive Advantages

 

The Mellanox Spectrum-2 SN3420 isn’t just another switch. It delivers tangible efficiencies that set it apart in crowded data centers.

 

Cost Efficiency
With 48x 25G ports in just 1 rack unit, the SN3420 maximizes rack space. Compared to switches offering only 32 ports per unit, it connects up to 50% more servers per rack. Fewer switches mean lower hardware costs, reduced power use, and simpler cabling. For businesses scaling 25G networks, this density slashes the total cost of ownership.

 

Future-Proofing
While many ToR switches max out at 40G uplinks, the Mellanox Spectrum-2 SN3420 includes 12x 100GbE ports ready for spine-layer upgrades. As networks evolve to 200G/400G cores, these uplinks prevent costly “forklift upgrades.” This means teams can start with 25G servers today, and then reuse the same switch when upgrading spine links in the future.

 

Unified End-to-End Stack
The Mellanox Spectrum-2 SN3420 isn’t standalone. NVIDIA’s full stack—ConnectX SmartNICs (server adapters), BlueField DPUs (data processing units), and LinkX cables—is engineered to work together. This integration boosts performance up to 30% for AI/ML and storage workloads versus mixed-vendor setups. The outcome? One ecosystem, seamless optimization.

 

6. Comparison with Other SN3000 Models

 

While the SN3420 excels as a leaf switch, NVIDIA’s Spectrum-2 family offers tailored solutions for diverse roles. Here’s how they compare:

 

SN3420: The Density King\

Designed as a high-density top-of-rack (ToR) leaf switch, the NVIDIA Spectrum-2 SN3420 delivers maximum port density within a 1U form factor: 48x 25GbE server ports and 12x 100GbE uplinks. With 2.4 Tbps of throughput and splittable uplink flexibility, it provides an optimal upgrade path for data centers modernizing from 10G to 25G/100G server connectivity, offering high performance for cost-optimized deployments.

 

SN3700: AI/ML Powerhouse
Engineered for spine and super-spine deployments, the NVIDIA Spectrum-3-based SN3700 delivers 32x 200GbE ports and 6.4 Tbps throughput. With double the packet processing capacity (8.33 Bpps) of the SN3420, it efficiently manages high-volume traffic flows (“elephant flows”) in demanding AI training, HPC, and hyperscale cloud environments. Its non-blocking architecture ensures congestion-free operation for GPU-driven workloads.

 

SN3700C: The Port Multiplier
The NVIDIA Spectrum-3-based SN3700C switch delivers flexible port density in a 1U form factor. Its 32x 100GbE ports can be split into 128x 25GbE connections, providing 3.2 Tbps throughput. This versatility enables deployment as a high-density leaf switch for cost-optimized 25GbE server access or as an economical spine layer. The distinctive “any-to-any” port functionality—where any port operates as uplink or downlink—supports dynamic infrastructure requirements in cloud and containerized environments.

 

SN3750-SX: Telco Specialist
The NVIDIA Spectrum-3-based SN3750-SX switch matches the SN3700’s core specifications—32x 200GbE ports and 6.4 Tbps throughput—while integrating carrier-critical features: hardware-accelerated Precision Time Protocol (PTP), Synchronous Ethernet (SyncE), and secure boot. Optimized for 5G Radio Access Networks (RAN) and edge deployments, it delivers the precision timing, security, and resilience required for NVIDIA CloudRAN solutions and other latency-sensitive telco workloads.

 

Model	Role	Ports	Throughput	Target Use Case
SN3420	ToR Leaf	48x25G + 12x100G	2.4 Tb/s	General-purpose DC
SN3700	Spine/ Super-Spine	32x200G	6.4 Tb/s	AI/ML/HPC clusters
SN3700C	Flexible Spine	32x100G (splittable)	3.2 Tb/s	High-density 10/25G leaf
SN3750-SX	Telecom Spine	32x200G	6.4 Tb/s	5G RAN, CloudRAN

 

 

7. Limitations

 

While powerful, the Mellanox Spectrum-2 SN3420 has constraints to consider. These reflect its position in NVIDIA’s broader product lineup.

 

No Native 400G Support
The SN3420 uses NVIDIA’s Spectrum-2 ASIC (the core processing chip). Unlike newer Spectrum-3 switches (like the SN4600C), it cannot support 400G ports. If you plan to upgrade to 400G spine networks within 2–3 years, you may need to replace leaf switches later. That said, 400G remains overkill for most 25G server racks today.

 

100G Uplink Cap
All 12 uplinks max out at 100G per port. Competing ToR switches (like Arista 7050CX3) offer 400G uplinks. For massive AI/ML clusters requiring 200G/400G spine connections, consider NVIDIA’s own SN3700 (200G) instead. For typical enterprise/cloud workloads though, 100G is still robust.

 

Conclusion

 

The NVIDIA Mellanox Spectrum-2 SN3420 proves that you don’t need to sacrifice performance for affordability in modern data centers. With its high-density 48x25GbE server ports and 12x100GbE uplinks, it delivers exceptional value for 25G server upgrades and 100G spine connectivity. This compact 1U switch packs enterprise-grade power into a budget-friendly package.

 

For cloud providers, enterprises modernizing infrastructure, or teams running HCI/storage workloads, the SN3420 hits a critical sweet spot. Its open software freedom (Cumulus, SONiC, Linux) cuts vendor lock-in costs. Advanced features like NVIDIA’s WJH telemetry slash troubleshooting time, while RoCE optimization accelerates AI and storage traffic.

 

Though it lacks 400G support (unlike newer Spectrum-3 switches), its 100G uplinks and 2.4Tbps throughput handle most real-world demands today. For organizations prioritizing current 25G/100G needs without overpaying for future-proofing, the SN3420 delivers tangible TCO savings. It’s a strategic tool—not just a switch—for building agile, cost-controlled networks.