2026-10-05

Best 2.5 Gigabit USB Ethernet Adapter for Raspberry Pi 5 NAS (Tested Throughput)

Any RTL8156-based USB-C 2.5GbE adapter will work on a Raspberry Pi 5 running a recent kernel — the driver is mainline, and the real throughput bottleneck is the Pi's NVMe storage, not the adapter. On my build, the NVMe drive tops out at 453 MB/s sequential read, which is well above the ~280 MB/s ceiling of a single 2.5 Gbps link, so the adapter won't be the limiting factor.

My Test Build

Here's exactly what I'm running:

• Board: Raspberry Pi 5 Model B Rev 1.1, 15 Gi RAM (the 16 GB SKU — reports as ~15 Gi usable)
• OS: Debian GNU/Linux 13 (trixie), kernel 6.18.34+rpt-rpi-2712
• NVMe: Fanxiang S501Q 512 GB (476.9 G formatted), booting directly from /dev/nvme0n1p2
• PCIe: Gen 2 (default — I haven't forced gen3)
• Storage benchmarks (fio): 453 MB/s sequential read, 438 MB/s sequential write, 16,433 IOPS random 4K read
• SoC temps: 49.4 °C idle, 48.8 °C after sustained load (yes, slightly lower under load — the active cooler ramps up)

The NVMe sits on the Pi 5's single PCIe 2.0 x1 lane, which maxes out around 450–500 MB/s. My 453 MB/s read confirms I'm close to that ceiling. A 2.5 Gbps Ethernet link tops out at roughly 280 MB/s after protocol overhead, so storage will never be the bottleneck for a single 2.5G adapter. That's important context for everything below.

Why 2.5GbE on a Pi 5?

The Pi 5's built-in Ethernet is Gigabit — about 117 MB/s in practice. A USB 2.5G adapter plugged into one of the two USB 3.0 ports nearly triples your network throughput. Since USB 3.0 offers 5 Gbps, there's enough bus bandwidth for one 2.5G adapter without contention, though you do share that bus with the other USB 3.0 port.

For a Samba or NFS NAS serving a few users on a 2.5G home network, this is the cheapest meaningful upgrade you can make.

The Adapters Worth Considering

I have not personally benchmarked each of the following adapters. What I can tell you is which chipset to look for and what to expect based on published specs and broad community reports.

The Chipset That Matters: RTL8156B

Almost every sub-$20 USB-C 2.5G adapter uses a Realtek RTL8156B. The Linux kernel (certainly by 6.6+, and my 6.18 kernel handles it without issue) includes the r8152 driver, which supports this chipset natively. No out-of-tree drivers, no firmware blobs. If the adapter uses RTL8156B, it will work on your Pi 5.

Specific Products

• Cable Matters USB-C to 2.5G Ethernet Adapter — Reportedly RTL8156B-based. Compact dongle form factor. Widely available and usually the cheapest option at around $14–16.
• UGREEN USB-C 2.5G Network Adapter — Also RTL8156B-based per teardowns. Slightly more robust build with an aluminum shell. Typically $15–18.
• TRENDnet TUC-ET2G USB-C 2.5G Adapter — TRENDnet lists RTL8156 compatibility. Marginally more expensive (~$19), sometimes preferred for the brand's networking pedigree.
• Plugable USB-C 2.5GbE Adapter — Plugable explicitly documents Linux support and uses RTL8156B. Usually around $16–18.

Honest take: These are functionally identical. They use the same chipset, the same driver, and will deliver the same throughput. Buy whichever is cheapest or in stock. The performance differences between them, if any exist, are within measurement noise.

What About USB-A Versions?

If you'd rather keep your USB-C port free (for example, for power delivery with a high-quality cable like our 240W USB-C Fast-Charging & Data Cable – Braided, LED Indicator), all four brands above also sell USB-A variants. The Pi 5 has two USB 3.0 Type-A ports. Same chipset, same driver, same speeds. Just a different plug.

Expected Real-World Throughput

I did not run iperf3 through each of these four adapters — I'm being straight about that. Based on what the Pi 5's USB 3.0 bus can deliver and what the community consistently reports with RTL8156B adapters on Linux:

• iperf3 (network only): ~2.35 Gbps (~280 MB/s) is typical
• Samba large-file transfer: ~230–260 MB/s is realistic after SMB overhead
• NFS sequential read: ~250–270 MB/s is commonly reported

My NVMe delivers 453 MB/s sequential read — more than enough headroom. If you're using a USB-attached SSD instead of NVMe, your storage might become the bottleneck before the network adapter does.

NVMe Boot: Why It Matters Here

Booting from NVMe (as I do from /dev/nvme0n1p2) keeps the USB bus entirely free for the Ethernet adapter. If you boot from a USB SSD, you're sharing USB 3.0 bandwidth between storage and network — both competing for that 5 Gbps pipe. NVMe boot eliminates that contention entirely.

If you have a spare NVMe drive and want an external enclosure for cloning or backup purposes, something like our M.2 NVMe SSD Enclosure – USB-C 10Gbps with Magnetic Closure is handy for initial imaging, though you wouldn't want to run your NAS storage through USB when you have a PCIe slot available.

Thermal Notes

My Pi 5 sits at 49.4 °C idle and actually dropped to 48.8 °C under sustained storage load — the active cooler does its job. Adding a USB Ethernet adapter introduces a few hundred milliwatts of extra power draw but I observed no meaningful SoC temperature increase. The adapters themselves get warm (reportedly 45–55 °C on the adapter casing under sustained transfer), which is normal for a passively cooled RTL8156B.

Over time, dust accumulation on the Pi's fan can degrade cooling. If you're running this 24/7 as a NAS, something like JAKEHOE Fan Cleaner – Dust Removal Tool for Server & NAS Fans saves you from disassembly during maintenance.

Who Should NOT Do This

• If your home network is still Gigabit everywhere, a 2.5G adapter gains you nothing. Upgrade your switch first.
• If you need more than ~260 MB/s sustained to multiple clients, a Pi 5 NAS isn't the right platform. Look at an x86 mini-PC or a small VPS like Hetzner Cloud for remote storage needs.
• If you plan to attach two 2.5G adapters (bonding/LACP), USB 3.0 bandwidth becomes a real constraint and you'll see diminishing returns. One adapter is the sweet spot.

Verdict

Buy any RTL8156B-based USB-C 2.5G adapter — Cable Matters, UGREEN, TRENDnet, Plugable, or a no-name with the same chipset. They all use the same silicon, the same mainline Linux driver, and will deliver roughly 230–260 MB/s real Samba throughput on a Pi 5 with NVMe storage. Boot from NVMe to keep the USB bus free, and spend the money you saved on a 2.5G switch instead of a premium adapter brand.