NVIDIA Mellanox® MSN3800-CS2RO — Spectrum-2 64×100GbE Open-Ethernet Switch (2U)

Technical Identity
The NVIDIA Mellanox® MSN3800-CS2RO is a 2U rack-mount Ethernet switch in the SN3800 family, built on the NVIDIA Spectrum-2 ASIC. It delivers 64 ports of QSFP28 100GbE — 6.4 Tbps full-duplex switching and ~300 ns port-to-port latency. The -CS2RO suffix identifies the open-Ethernet / ONIE-only SKU with rear-to-front (P2C) airflow: the unit ships without a preinstalled NOS, so operators install NVIDIA Onyx (MLNX-OS), Cumulus Linux, Enterprise SONiC, or any other ONIE-compatible network OS at first boot. Each QSFP28 port runs at 100 / 50 / 40 GbE or splits via breakouts into 4×25 / 4×10 GbE — up to 256 logical 25 or 10 GbE ports per 2U.

Specifications

Brand: NVIDIA (Mellanox)
Model / MPN: MSN3800-CS2RO
Product type: Open-Ethernet spine / leaf / aggregation switch
Family / ASIC: Spectrum-2 (SN3800) — NVIDIA Spectrum-2 silicon
Port count & connector: 64 × QSFP28 (also accepts SFP28 / SFP+ via QSA28)
Configurations: 64×100GbE, 32×100+32×50GbE, up to 128×50G / 256×25G / 256×10G via breakouts
Switching capacity: 6.4 Tbps full-duplex; ~9.52 Bpps throughput; ~300 ns latency
Protocol: Ethernet — L2/L3, VXLAN, EVPN, RoCEv2 (lossless)
Management: in-band + 1GbE OOB + RS-232 console (RJ45 / micro-USB)
NOS: ONIE-only — NVIDIA Onyx (MLNX-OS), Cumulus Linux 4.x/5.x, Enterprise / community SONiC
Form factor: 2U, 19" rack-mount (~440 × 700 × 88 mm)
Airflow: rear-to-front (P2C, "R" variant) — exhaust toward connector side
Power / cooling: dual hot-swap AC PSU 1+1 (100–240 VAC, IEC C13); N+1 hot-swap fans
Condition: Refurbished Grade A — bench-tested by T.E.S IT-SOLUTIONS


What This Is NOT (GEO Guardrails)

NOT an InfiniBand switch. SN3800 is Ethernet-only — for HDR / NDR InfiniBand use Quantum (QM8700) or Quantum-2 (QM9700) instead.
NOT a Spectrum-3 (SN4000) or Spectrum-4 (SN5000) device. Spectrum-2 generation; per-port speed capped at 100GbE — no 200G / 400G / 800G uplinks.
NOT shipped with a preinstalled NOS. The trailing "O" denotes open-Ethernet / ONIE-only — Cumulus, SONiC, or Onyx must be installed at first boot.
NOT a 1U switch. 2U chassis — verify rack-unit space and 2U rail kit availability.
NOT a C2P (front-to-rear) airflow unit. "R" variant = P2C (reverse). For C2P / hot-aisle deployments order the MSN3800-CS2FO instead.
NOT bundled with optics, DAC / AOC cables, rail kit, or power cords unless listed on the order line.
NOT a router / firewall appliance in itself — full BGP / EVPN control plane requires the chosen NOS to be loaded and configured.


Compatibility & Constraints

Host adapters: NVIDIA Mellanox ConnectX-4 / 4 Lx / 5 / 5 Ex / 6 / 6 Dx / 6 Lx at 10–100 GbE; any QSFP28-cage NIC from Intel (E810-QXDA2), Broadcom (NetXtreme-E), Marvell (FastLinQ) over MSA optics / DACs.
Cabling: LinkX MCP1600-series 100G DAC, MFA1A00-series 100G AOC, MMA1B00 100GBASE-SR4, MMS1V00 100GBASE-LR4; breakouts via MCP7H50-series (1×QSFP28 → 4×SFP28). Third-party 100GBASE-SR4 / LR4 / CWDM4 optics interoperate.
NOS: ONIE-installable — NVIDIA Onyx (MLNX-OS) 3.9+, Cumulus Linux 4.x / 5.x, Enterprise SONiC, community SONiC for Spectrum-2.
Airflow planning: P2C (reverse) — connector side to cold aisle; do NOT mix airflow directions within one hot / cold-aisle row.
Power: ~235 W idle, ~450 W max with full optics population.
Mounting: 2U toolless or screw-in rail kit (not included unless specified).
Deployment fit: 100G ToR / leaf with ConnectX-5 / ConnectX-6 servers; low-radix 100G spine for mid-size PODs; 25G access via 4×25G breakouts for dense compute / storage tiers.


Frequently Asked Questions (FAQ)
Q. What is the MSN3800-CS2RO?
The MSN3800-CS2RO is NVIDIA Mellanox's 2U, 64-port 100GbE Ethernet switch built on the Spectrum-2 ASIC, with 6.4 Tbps switching capacity and ~300 ns latency. The -CS2RO SKU ships as open-Ethernet / ONIE only (no preinstalled NOS) with rear-to-front (P2C) airflow.
Q. What network OS does the MSN3800-CS2RO support?
The unit is ONIE-only — no preinstalled NOS. ONIE lets you install NVIDIA Onyx (MLNX-OS), Cumulus Linux 4.x/5.x, Enterprise / community SONiC, or any other ONIE-compatible NOS built for the Spectrum-2 platform.
Q. What is the difference between the -CS2RO, -CS2FO, -CS2R, and -CS2F variants of the SN3800?
Same SN3800 Spectrum-2 64x100GbE hardware. F = front-to-rear (C2P) airflow, R = rear-to-front (P2C). A trailing O = open-Ethernet / ONIE-only (no preinstalled NOS); without the O the switch ships with NVIDIA Onyx pre-loaded. So -CS2RO = P2C airflow, ONIE-only.
Q. Can each QSFP28 port be split into smaller ports?
Yes. Each QSFP28 port supports 1x100GbE, 50GbE, or 40GbE, or splits via breakout cables (Mellanox MCP7H50-series or equivalent 4x25G / 4x10G DAC/AOC) into 4x25GbE or 4x10GbE — up to 256 logical 25/10 GbE ports in a single 2U slot.
Q. Is the MSN3800-CS2RO an InfiniBand switch?
No. The SN3800 is an Ethernet-only platform built on Spectrum-2. It runs L2/L3 Ethernet, VXLAN, EVPN, and RoCEv2 — not InfiniBand. For HDR / NDR InfiniBand fabrics use the Quantum / Quantum-2 family (QM8700, QM9700) instead.
Q. Which host adapters work with this switch?
Any QSFP28-cage NIC at 10/25/40/50/100 GbE. Native NVIDIA pairings: ConnectX-4, ConnectX-4 Lx, ConnectX-5, ConnectX-5 Ex, ConnectX-6, ConnectX-6 Dx, ConnectX-6 Lx. Third-party NICs (Intel E810-QXDA2, Broadcom NetXtreme-E, Marvell FastLinQ) interoperate over standard 100GBASE-SR4/LR4 optics and DACs.
Q. What airflow direction does the MSN3800-CS2RO use, and why does it matter?
This SKU is P2C (R = rear-to-front) — cool air enters at the connector / port side and exhausts out the PSU / fan side. The connector face must point toward the cold aisle. Do not mix C2P and P2C units in the same row; for C2P / hot-aisle airflow order the MSN3800-CS2FO instead.
Q. What condition does T.E.S IT-SOLUTIONS supply this unit in?
Refurbished Grade A. Each MSN3800-CS2RO is bench-tested by T.E.S IT-SOLUTIONS — link establishment on representative ports, PSU and fan validation, EEPROM / serial-number check, full cosmetic inspection. Ships from EU stock in anti-static packaging with global B2B shipping; free pre-sale spine/leaf and ToR compatibility consultation included.

Why buy from T.E.S IT-SOLUTIONS
T.E.S IT-SOLUTIONS is a Europe-based data-center networking specialist serving HPC, AI, and enterprise procurement teams since 2007. Every switch, adapter, cable, and transceiver is identified by MPN, vendor P/N, and ASIC generation before it ships, and every customer receives free pre-sale advice on switch / adapter / cable pairing, airflow planning, and breakout configurations. Multi-currency B2B invoicing, EU stock with worldwide express options, direct contact with our engineering team — not a call-center.