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The 10Gtek RTL8125-2.5G-4T-X4 is a PCIe card with four 2.5GbE Ethernet ports, but its independent review did not establish that all four ports can sustain full line rate simultaneously. ServeTheHome’s iperf3 testing found two to three ports could run at full speed; its four-port test was harder on the test harness, with reported speeds above 2Gbps per port. It is a better fit for adding several network interfaces than for maximizing aggregate throughput.
What the 10Gtek RTL8125-2.5G-4T-X4 includes
The card provides four RJ-45 ports, each based on a Realtek RTL8125BG controller, plus an ASMedia ASM1812 PCIe hub. In other words, this is four network controllers connected through a hub, not one four-port Ethernet controller. 10Gtek lists the host interface as PCIe 2.1 x4; ServeTheHome describes it as PCIe Gen2 x4. Those descriptions come from different sources and should not be collapsed into a single vendor specification.
10Gtek’s listing includes both full-height and low-profile brackets. Check your case and available slot before buying, and make sure the motherboard has a suitable PCIe slot for the card’s x4 interface.
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Can all four ports run at full speed together?
ServeTheHome says it purchased and tested the card with its iperf3 setup. In those tests, two to three ports could be pushed at full speed. The four-port test load was more challenging for the test harness, and the reviewer reported speeds above 2Gbps per port. The review proposed that the ASM1812 and PCIe Gen2 x4 link were probably responsible for the less-than-ideal aggregate result, but this was an explanation, not a controlled demonstration of a universal bottleneck.
#1 Best Overall
- Controller(s)：Realtek RTL8125BG + ASMedia ASM1806.
- Single RJ-45 Port.
- PCIe2.0, x1 Lane.
- Support PXE, VLAN, Jumbo Frames. Not-support WOL, DPDK, iSCSI, FCoE.
- Compatible with Windows 7/8/10/11, Windows Server 2008 R2/2012/2016/2019, Linux 2.6.x to 5.x, Centos 6/7/8, Ubuntu 16/18/19/20, VMware ESXi 6. NOT SUPPORT ESXI 7/8, FREEBSD and HOT SWAPING.
The practical answer is that the review supports the card as a way to add multiple useful interfaces, but it does not prove that every port will deliver full line rate simultaneously in every computer and workload. If your main goal is aggregate throughput, ServeTheHome recommends considering a 10GbE card instead. Compare the host slot, expected traffic pattern and required port count against your own workload rather than treating the review’s results as a guaranteed limit or guarantee.
Port mapping and enumeration
On ServeTheHome’s test system, plugging a cable into the end port brought up the third enumerated NIC rather than the first or fourth. The reviewer described this as a small but potentially annoying mapping issue. It is an observation from that setup, not evidence that every operating system or system will enumerate the ports the same way. For installations that depend on fixed interface names, verify port-to-interface mapping after installation.
Rank #2
- 【Controller】:2.5GbE PCI-E NIC with Original Realtek RTL8125BG controller.
- 【Data Rate】:Single copper RJ45 port(100MbE/1GbE/2.5GbE) let you connect to network cable for meeting the demands of data center environments.PCIe v2.0 x1; X1/X4/X8/X16 Lane.
- 【Technical Support】:Jumbo Frames;PXE;DPDK;WOL;VLAN;Wake on LAN.
- 【Supported Operating Systems】: Windows, Windows Server, Linux*RHEL, Ubuntu, DOS, MAC OS, OpenWrt ESXI6.7,ESXI8.0 (Doesn't support ESXI 7.0, ESXI6.5), etc.
- 【What you Get】: Vogzone 2.5GbE PCI-E X1 Network Card RTL8125B-2.5G (compare to Realtek RTL8125B) x1, Low-profile Bracket x1.
Operating-system support and drivers
10Gtek lists support for Windows 7, 8, 10 and 11; Windows Server 2008 R2, 2012, 2016 and 2019; Linux kernel 2.6.x to 5.x; CentOS 6, 7 and 8; Ubuntu 16, 18, 19 and 20; and VMware ESXi 6. These are the manufacturer’s stated compatibility claims, not independent test results for every listed version. The product page lists older OS versions, so verify the current driver against your exact operating system or kernel before relying on compatibility.
The manufacturer explicitly says the card does not support ESXi 7 or 8, FreeBSD, or hot swapping. Its current download index maps this model to RTL8125BG, and its documentation page lists an RTL8125 driver and a “Quart port 2.5G NIC Driver,” both dated November 21, 2022. Check 10Gtek’s download index and 2.5G network card documentation page for applicable downloads and details.
Rank #3
- Equipped with original Intel X540 controller chip which supports Intelligent Offloads and make the servers more stable.
- Compatible with Windows Server 2003/ 2008/ 2012, Windows7/8/10*/Visa, Linux, ESX/ESXi*. Storage over Ethernet: iSCSI, FCoE, NFS. (Note that this card can be used with Windows 11, but it needs to be manually set up. If you buy it for Windows 11, please contact us for installation guide before using.)
- Dual copper RJ45 ports let you connect to Category-6A and up to 100m((Category-6 up to 55 m) for meeting the demands of data center environments. PCI Express* 2.1. 5.0 G T/s X8 Lane is suitable for both PCI-E X8 and PCI-E X16 slots.
- With profile bracket and additional low profile bracket that makes it easy to install the card in a small form factor/low profile computer case/server.NOT support hot swaping.
- What You Get: 10Gtek 10GbE PCI-E X8 Network Card X540-10G-2T (compare to Intel X540-T2) x1, Low-profile Bracket x1. Backed by 10Gtek 30 Days Free-returned, 3 Year Free Warranty and Lifetime Technology Support.
Features: supported and excluded
According to 10Gtek, the card supports Jumbo Frames, Wake-on-LAN (WOL), DPDK, iSCSI and FCoE. The manufacturer lists PXE and VLAN as unsupported. If your setup requires VLAN tagging or PXE boot, this model does not meet that stated requirement; confirm that the other listed features fit your configuration before purchase.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Price and who should consider it
10Gtek’s store listed the RTL8125-2.5G-4T-X4 at $55.99 when accessed on October 5, 2026. Price and availability can change, so check the manufacturer’s product listing before ordering.
Rank #4
- Compatible with Windows Server 2003/ 2008/ 2012, Windows7/8/10*/Visa, Linux, ESX/ESXi*. Storage over Ethernet: iSCSI, FCoE, NFS. (Only by setting up Win10 driver correctly the NIC can work on Win11! See the main picture for more detail of installation.)
- Equipped with high quality original Intel 82599ES controller which supports I/O virtualization and make the servers more stable.
- Supports 10G, not support 1G/2.5G/5G; Dual SFP+ ports let you connect to 10 Gigabit SFP+ module/DAC/AOC for meeting the demands of data center environments. PCI-E X8 Lane is suitable for both PCI-E X8 and PCI-E X16 slots.
- With profile bracket and additional low profile bracket that makes it easy to install the card in a small form factor/low profile computer case/server.NOT support hot swaping.
- What You Get: 10GbE PCI-E X8 Card X520-10G-2S x1, Low-profile Bracket x1, 30 Days Free-returned, 3 Year Warranty and Lifetime Technology Support. PS: Due to the particularity in QNAP/Synology, for QNAP/Synology users, pls contact us before purchase.
At that listed price, the card may appeal to someone who needs several 2.5GbE interfaces in one PCIe slot and is comfortable checking drivers and port mapping. It is less compelling when the deciding factor is maximum simultaneous throughput, a supported ESXi 7/8 or FreeBSD configuration, hot swapping, PXE or VLAN. If comparing other cards, weigh port count, per-port rate, host PCIe requirements, workload-level aggregate throughput, OS support, required features, bracket height and total system cost; the cited review does not provide a controlled comparison with named alternatives.
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Quick Recap
Best Value
- QUAD 2.5G RJ45 PORTS: 4X Intel I226-V controllers with PCIe packet switch, PCIe 2.0 x4 uplink, auto-negotiating 2500/1000/100/10Mbps for multi-WAN firewalls, VLANs and NVR.
- SOFT ROUTER & FIREWALL READY: Supports Proxmox VE, ESXi 7.0/8.0, Hyper-V, OpenWrt and pfSense/OPNsense — use the latest system release for the best I226-V experience.
- DRIVER-FREE EXPERIENCE: In-box drivers for Windows 10/11 and Windows Server 2019-2025; native igc driver on Linux 5.15+; keep Proxmox kernel up to date for best VM throughput.
- LOW CPU OFFLOADING: RSS, TCP/UDP checksum offload, TSO v2, 9.5KB jumbo frames and IEEE 802.3az EEE keep CPU usage low during SMB/NFS transfers and 24/7 routing.
- RELIABLE 24/7 OPERATION: 1.3W per port with passive heatsink, IEEE 1588 time sync and UEFI PXE boot for diskless deployment; GLOTRENDS support with driver updates.
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.
