The ConnectX-4 Lx is a SFP28 10GbE adapter from Mellanox (now NVIDIA), on PCIe 3.0 x8, using the mlx5 driver that ships in the mainline Linux kernel. It is end-of-life at its maker, which means no new firmware - not that it has stopped working. 2 listings in stock, from $170.00.
Prices updated · live figures update every 4-5 hours
Thin coverage today - fewer than three listings, so this page is not indexed until stock returns.
Passive direct-attach copper, by length. A DAC is a fixed-length cable with the transceivers moulded on - you buy the whole run at once rather than a cable plus two modules.
Every "compatible with" phrase below is the seller's own wording, recorded as a claim and badged. We have not tested any module against any switch.
| Module | Type | Brand | Seller compatibility claims | Price | |
|---|---|---|---|---|---|
| SFP28 25GBASE-SR module | 25GBASE-SR | 10Gtek | none stated | $15.99 | Buy |
| SFP28 25GBASE-SR module | 25GBASE-SR | 10Gtek | none stated | $15.99 | Buy |
| SFP28 25GBASE-LR module | 25GBASE-LR | 10Gtek | none stated | $18.39 | Buy |
| SFP28 25GBASE-SR module | 25GBASE-SR | 10Gtek | none stated | $19.99 | Buy |
| SFP28 AOC | AOC | 10Gtek | none stated | $19.99 | Buy |
| SFP28 AOC | AOC | ipolex | 25GBase Active Optical Cable, 25Gbps SFP28, SFP28-25G-AOC5Mseller claim | $30.39 | Buy |
| SFP28 AOC | AOC | 10Gtek | none stated | $33.59 | Buy |
| SFP28 AOC | AOC | 10Gtek | none stated | $37.99 | Buy |
The ConnectX-4 Lx uses the mlx5 driver rather than mlx4, and mlx5 is the actively maintained branch that also carries every newer NVIDIA adapter - a real advantage over the ConnectX-3 generation. What it no longer is: the two cards are now both formally end-of-life at NVIDIA, confirmed from NVIDIA's own current documentation rather than assumed from age. See the lifecycle section below for exactly what that does and does not mean for a purchase today.
The SFP28 cages on these cards are the interesting part. SFP28 is the 25G form factor and it is backward compatible with SFP+, so a ConnectX-4 Lx will happily run a 10G link with a 10G direct-attach cable while leaving 25G available if the other end ever supports it. For a home build that is optionality rather than a benefit today, but it is optionality that costs nothing.
The price reflects the newer generation. These cards sit meaningfully above ConnectX-3 in our tables, and for a straightforward two-machine 10GbE link the older card does exactly the same job. The case for spending the difference is the actively maintained mlx5 driver rather than anything you will observe in use.
One practical note: 25G direct-attach cables are a different product from 10G ones, and our tables label them separately for that reason. A 25G SFP28 cable will work at 10G, but if you are building a 10G link there is no reason to pay for one. And if 25G is what you are actually after, this card's own SFP28 cage is real 25GbE-capable hardware - see the 25GbE cluster's card table for what a dedicated 25G build looks like priced against it.
ConnectX-4 and later use the mlx5 driver, which is in the mainline Linux kernel and is actively maintained - a meaningful difference from the mlx4 generation, and unaffected by the product line's own commercial end-of-life status below. That matters more than any marketing claim, because a card whose driver is in the mainline kernel is a card your Linux-based NAS or hypervisor recognises without you doing anything.
We state in-kernel driver names as documented facts because they are - they come from the kernel's own driver documentation, not from a forum thread reporting that something worked. Where community experience is the only evidence available for something, we say so rather than dressing it up.
NVIDIA's ConnectX-4 Lx user manual now states plainly: "The ConnectX-4 Lx product line has moved to end-of-life" (confirmed 2026-09-13). That is a change from this card's earlier positioning as the non-EOL alternative to the ConnectX-3 - it no longer is one. NVIDIA's own kernel release notes, dated the same year, still list mlx5 as actively supporting this card, so the driver situation is unchanged even though the commercial one is not. Those are two different questions and conflating them is the most common error in discussions about this card.
Windows support is a separate question from Linux support and varies by card age. Check the maker's current driver page for your specific part number before buying if Windows is the target, because an in-kernel Linux driver tells you nothing about it.
OEM-branded ConnectX-4 Lx cards exist in the same way and the same crossflashing considerations apply, though the supply is thinner because these cards are newer and fewer have been retired.
The general shape of the crossflash question is the same across every card in this category: an OEM board carries the server maker's firmware, that firmware sometimes behaves differently from the silicon vendor's, and there is a community practice of replacing it. We link the maintained community documentation rather than reproducing the procedure here. A stale copy of a flashing guide is actively dangerous, and the people who maintain the canonical versions do so because the details change.
If you are buying an OEM-branded card specifically because it is cheaper, factor in the possibility that you will need to do this. If that prospect does not appeal, the vendor-branded card at a higher price is buying you the absence of that job.
This is a SFP28 card, so the port is a cage rather than a socket and you choose what goes in it. For two machines near each other, a passive direct-attach copper cable is the cheapest, coolest and simplest answer, and it is what most builds using this card should use.
For longer runs you need optics - a module at each end plus a fibre between them - or an active optical cable, which packages the same thing as a single sealed object. Both cost more than direct-attach copper and both go much further.
The compatibility question belongs here rather than being buried. Third-party module sellers list the equipment they claim compatibility with, and those are claims we record and badge rather than verify. Vendor coding is a documented phenomenon: cards and switches can and do refuse modules that do not identify as approved parts. A direct-attach cable avoids the entire question, which is another reason it is the default recommendation for a two-machine build.
The cabling guide covers every SFP28 DAC, AOC and optic in one place · The 10GbE hub compares every card we track and covers the SFP+ versus 10GBASE-T decision · the two-machine build prices two of these plus a cable, with no switch · used servers almost always have a spare PCIe slot for one · NAS devices is usually what sits at the other end · rack disk shelves are the other common thing on the far end of a fast link.
For a plain 10GbE link between two machines, the older card does the same job for less. Both cards are now formally end-of-life at NVIDIA - the ConnectX-4 Lx's earlier advantage there no longer holds. What it still has is the actively maintained mlx5 driver rather than the mlx4 generation, which is a real hedge on driver longevity even though the product line itself is not being sold new.
Yes. SFP28 is backward compatible with SFP+, so the card runs a 10G link with an ordinary 10G direct-attach cable. You do not need 25G cabling and there is no reason to buy it for a 10G build.
mlx5, in the mainline Linux kernel and actively maintained. It is the same driver family that carries NVIDIA's current adapters, which is the main practical argument for this card over the ConnectX-3.
These are PCIe 3.0 x8 cards. Check the slot you intend to use - a physically x16 slot that is electrically x4 is common on consumer boards, and it is the kind of detail that is easier to confirm before purchase than after.
Almost never today, and the honest answer is that you are buying an SFP28 card for the driver support rather than the speed. If the storage on either end cannot saturate 10G - which is the usual situation - then 25G is a number on a box.
Yes, though fewer than for the ConnectX-3 because the generation is newer and less of it has been retired from service. The same firmware considerations and the same community crossflashing practice apply.
Specification claims on this page were checked against the pages below on 4 August 2026. Where a widely-repeated figure did not survive that check, we report what the source says now and say so in the text rather than repeating the familiar number.