The QNAP QXG-25G2SF-CX6 is a dual-port SFP28 network card for 10GbE or 25GbE links, built around NVIDIA’s ConnectX-6 Lx controller. Its strongest case is adding high-speed networking to a compatible QNAP NAS; for a general server, the historical $399 list price cited by ServeTheHome makes compatibility, support, and actual need for two 25GbE ports central to the value decision. That price is from the review published September 11, 2025, not a current quote.
What the QXG-25G2SF-CX6 offers
QNAP specifies a PCIe Gen4 x8 interface, two SFP28 ports, and 10Gbps/25Gbps transmission rates. ServeTheHome’s review says the card can also run at PCIe Gen3 speeds; QNAP describes backward compatibility with Gen3 and Gen2. Neither statement means every host slot will deliver full link performance: check available lane width, slot configuration, system support, and the target operating system before buying.
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The card is low-profile in size and includes a small fan. ServeTheHome reports that the package includes low-profile and full-height brackets, plus a specialized bracket for selected QNAP NAS units. QNAP lists capabilities including SR-IOV, RoCE, NFS over RDMA, VLAN features, and network offloads. These are feature claims, not a guarantee that a given workload will benefit; practical availability depends on system support, operating system, driver, firmware, and network configuration.
Compatibility: check the host before ordering
For a QNAP NAS
QNAP positions the card for NAS expansion, but compatibility is model- and software-dependent. Use QNAP’s product page and its supported NAS information to confirm the exact NAS model and current operating-system version. The specialized bracket is for selected QNAP NAS units, not a universal fit.
#1 Best Overall
- Equipped with Intel E810-XXVAM2 controller
- Dual 25GbE (supports 10Gbps) ports allows connecting to multiple high speed networking devices
- PCIe Gen 3 x8 (compatible with PCIe x4, x1, up to x4 slots are recommended)
- Supports Port Trunking to combine both ports to achieve up to 50 Gbps transfer speeds for accelerating file sharing and intensive data transfer
- Forward Error Correction (FEC) ensuring reliable data transfer enterprise-level networks
For a Windows or Linux system
QNAP says Windows and Linux operation requires a driver. Confirm driver availability for the specific OS version and verify that the motherboard or server provides a suitable PCIe slot with the needed lane configuration. A card fitting physically does not by itself establish operating-system or feature compatibility.
What cable or transceiver does it need?
The two ports are SFP28 cages, so the link medium must suit both the card and the device at the other end. ServeTheHome says the card can use DAC cables or optics and can operate at 10Gbps as well as 25Gbps. Check the supported speed and media at both ends rather than assuming any SFP28 module or cable will work in every topology.
QNAP’s hardware specifications name these relevant accessories: CAB-DAC30M-SFP28 and CAB-DAC15M-SFP28 DAC cables, and the TRX-25GSFP28-SR optic. Select a cable or optic based on the endpoints and link design; these are optional, topology-dependent accessories, not required purchases for every setup.
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Rohit Kumar’s ServeTheHome review, published September 11, 2025, reports iperf3 performance broadly in line with expectations for an updated 25GbE NIC. The review observed 11–16W at the PDU with DACs and estimated approximately 10–15W at the card. Those figures are the reviewer’s test observations, not QNAP specifications or independently reproduced measurements here; the review notes that optics could add a few watts.
Rank #2
- Equipped with Intel’s X710 Ethernet Controller
- Dual 10GbE (10G/5G/2.5G/1G/100M) ports allows connecting to multiple high speed networking devices
- PCIe Gen 3 x4 (compatible with PCIe x4, x1, up to x4 slots are recommended)
- Supports Port Trunking to combine both ports to achieve up to 20 Gbps transfer speeds for accelerating file sharing and intensive data transfer
- Supports SR-IOV and iSCSI to greatly boosts network efficiency and is ideal for I/O-intensive and latency-sensitive virtualization applications and data centers
The review identified price as the main drawback, giving a $399 list price at publication and contrasting it with substantially cheaper older ConnectX-4 Lx cards. Kumar wrote, “There is, however, a big ‘gotcha’ with this card: the price.” Treat $399 as dated review context from September 2025 and check the current listing before making a purchase decision.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is it worth buying?
The case is strongest when the card’s two 25GbE ports, QNAP NAS integration, and support for the exact host justify paying more than for an older or less integrated alternative. If you are adding networking to a general-purpose server, weigh that premium against your actual requirements rather than assuming the newer controller or listed offloads will improve every workload.
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- 10GbE/25GbE link requirements and the available PCIe generation and lane width.
- Exact NAS or server compatibility, OS version, driver support, and any required offloads.
- DAC or optic compatibility at both link endpoints.
- Physical clearance, bracket fit, and airflow around a card with a small fan.
- Measured power in a comparable setup and the current purchase price.
For a compatible QNAP NAS deployment, the supported fit may be the point of the premium. For other hosts, verify each compatibility and media detail and compare current alternatives; the ServeTheHome review provides context on older ConnectX-4 Lx cards but not a complete current shortlist.
Quick Recap
Sources
- ServeTheHome: QNAP QXG-25G2SF-CX6 25GbE NVIDIA ConnectX-6 Lx NIC Mini-Review, Rohit Kumar, September 11, 2025.
- ServeTheHome review, page 2, with performance, power, NAS use, and price discussion.
- QNAP QXG-25G2SF-CX6 Hardware Specs.
- QNAP QXG-25G2SF-CX6 product page.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
