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The QNAP QXG-25G2SF-CX6 is a dual-port 10/25GbE SFP28 card built around NVIDIA’s ConnectX-6 Lx controller. Its strongest case is adding 25GbE to a compatible QNAP NAS or server with supported drivers and the right PCIe slot; its main trade-off is price. ServeTheHome listed it at $399 in its September 11, 2025 review, so treat that as dated context—not a current quote.
What the QXG-25G2SF-CX6 offers
QNAP specifies a PCIe Gen4 x8 interface, two SFP28 ports, and 10Gbps or 25Gbps transmission rates. QNAP also describes backward compatibility with PCIe Gen3 and Gen2, while ServeTheHome notes the card can operate at PCIe Gen3 speeds. Actual throughput depends on the host slot’s generation and lane configuration, the system’s support, and the link at the other end. A slot that accepts the card does not by itself guarantee the card’s maximum rate.
The card is low-profile in size and includes a small fan. According to ServeTheHome, it ships with low-profile and full-height brackets, as well as a specialized bracket for selected QNAP NAS units. Check the card’s physical dimensions and bracket requirements against the intended chassis before buying.
What ServeTheHome found
In Rohit Kumar’s review, published September 11, 2025, ServeTheHome used iperf3 and reported results broadly in line with expectations for an updated 25GbE NIC. The review is the source of these test observations; they are not a separate test or a guarantee for every host, driver, or workload.
#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
ServeTheHome measured 11–16W at the PDU with DAC cables connected and estimated roughly 10–15W at the card. The review noted that optics could add a few watts. Those figures describe the review’s setup and should not be treated as manufacturer power specifications.
Will it work in your NAS or server?
Compatibility is more than having an open PCIe slot. Confirm the exact system model, slot wiring and available lanes, operating-system version, driver support, physical clearance, and bracket fit. QNAP’s compatibility and driver information can change, so check the current documentation for your system before ordering.
For a QNAP NAS
QNAP positions this as an expansion card for supported NAS models, and the specialized bracket may help with selected units. The supported-model list is not universal: verify your exact NAS model and current QTS or QuTS hero version on QNAP’s product page. The official-support and fit value may be especially relevant if you want a QNAP-listed upgrade rather than a generic server NIC.
For a Windows or Linux host
QNAP says Windows and Linux operation requires a driver. Confirm that an appropriate driver is available for your OS and intended configuration, and validate support for any advanced features you plan to use. QNAP lists features such as SR-IOV, RoCE, NFS over RDMA, VLAN functions, and network offloads, but their availability depends on operating system, driver and firmware versions, network configuration, and workload. A feature appearing on a product page does not ensure it is enabled or useful in every setup.
Choose the right SFP28 connection
The card has two SFP28 cages, so plan the media for both ends of each link. ServeTheHome says DAC cables or optics can be used and that 10Gbps operation is possible. QNAP lists the CAB-DAC30M-SFP28 and CAB-DAC15M-SFP28 DAC cables, and the TRX-25GSFP28-SR SR optic among relevant accessories. These are examples of listed options, not a requirement to buy QNAP-branded accessories for every topology.
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
- DAC: A direct-attach cable is a candidate when the device and switch or other endpoint are close enough and both ends support the chosen cable.
- Optics: An SFP28 transceiver and suitable fiber may fit a link where a DAC is not appropriate. Confirm the optic type and compatibility at both ends.
- 10GbE links: The review reports 10Gbps operation, but verify the specific module or cable, peer port, and configuration rather than assuming every combination negotiates as intended.
QNAP’s current hardware specifications and accessory details are available at the QXG-25G2SF-CX6 hardware specs page.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is the $399 review price worth it?
ServeTheHome stated a $399 list price in its September 11, 2025 review and identified price as the card’s main drawback, comparing it with substantially cheaper older ConnectX-4 Lx cards. That is a dated review price, not evidence of today’s retail price. Check current listings and compare the full cost of the card and required link media.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →The premium is easier to justify when the exact card’s QNAP compatibility, fit, or support matters to a NAS deployment. For a general server build, compare alternatives using the criteria that affect your setup rather than controller name alone:
- Two SFP28 ports and 10/25GbE support
- PCIe generation and lane availability in the target host
- NAS or operating-system compatibility and driver support
- DAC or optic compatibility at both link endpoints
- Need for advanced offloads or RDMA features
- Cooling, bracket, chassis clearance, and power draw
- Current purchase price, not a historical list price
For the review’s final pricing and NAS discussion, see ServeTheHome’s second review page. The complete review is at ServeTheHome.
Quick Recap
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.
