The ConnectX-3 is a SFP+ 10GbE adapter from Mellanox (now NVIDIA), on PCIe 3.0, using the mlx4 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. 5 listings in stock, from $27.99.
Prices updated · live figures update every 4-5 hours
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 | |
|---|---|---|---|---|---|
| SFP+ 10GBASE-SR module | 10GBASE-SR | QSFPTEK | none stated | $9.99 | Buy |
| SFP+ 10GBASE-SR module | 10GBASE-SR | 10Gtek | none stated | $11.89 | Buy |
| SFP+ 10GBASE-LR module | 10GBASE-LR | 10Gtek | none stated | $12.59 | Buy |
| SFP+ AOC 1m | AOC | 10Gtek | none stated | $13.29 | Buy |
| SFP+ 10GBASE-SR module | 10GBASE-SR | 10Gtek | none stated | $16.99 | Buy |
| SFP+ 10GBASE-LR module | 10GBASE-LR | 10Gtek | none stated | $17.99 | Buy |
| SFP+ AOC 1m | AOC | 10Gtek | none stated | $18.99 | Buy |
| SFP+ AOC 10m | AOC | 10Gtek | none stated | $19.99 | Buy |
| SFP+ AOC 5m | AOC | 10Gtek | none stated | $21.99 | Buy |
| SFP+ 10GBASE-T module | 10GBASE-T | H!Fiber | Cisco SFP-10G-T-S, D-Link, Merakiseller claim | $22.99 | Buy |
| SFP+ AOC 10m | AOC | 10Gtek | none stated | $23.99 | Buy |
| SFP+ AOC 20m | AOC | 10Gtek | none stated | $27.99 | Buy |
| SFP+ 10GBASE-T module | 10GBASE-T | H!Fiber | Cisco SFP-10G-T-S, D-Link, Merakiseller claim | $29.99 | Buy |
| SFP+ 10GBASE-T module | 10GBASE-T | 10Gtek | none stated | $31.49 | Buy |
| SFP+ 10GBASE-T module | 10GBASE-T | 10Gtek | none stated | $31.99 | Buy |
| SFP+ 10GBASE-T module | 10GBASE-T | 10Gtek | none stated | $39.99 | Buy |
| SFP+ 10GBASE-T module | 10GBASE-T | 10Gtek | Intelseller claim | $42.39 | Buy |
| SFP+ 10GBASE-T module | 10GBASE-T | 10Gtek | none stated | $44.99 | Buy |
| SFP+ 10GBASE-T module | 10GBASE-T | 10Gtek | none stated | $49.99 | Buy |
The ConnectX-3 is the card that made home 10GbE affordable, and it is still the default recommendation in most enthusiast threads for a reason: it was deployed by the million, it is the oldest card here, and consequently it is the cheapest way to get an SFP+ port into a machine.
It is also the card that generates the most anxiety, because it carries an end-of-life notice and people reasonably ask what that means for a purchase today. The answer separates two things that get conflated. The maker has stopped developing for it - that is what EOL means. Your operating system has not dropped it: the driver is in the mainline kernel tree, and drivers leave that tree slowly and with a deprecation cycle rather than overnight.
So the honest framing is about time horizon rather than function. For a machine you expect to rebuild or replace within a few years, this is a sound purchase and the price is hard to argue with. For something you intend to install once and never touch again for a decade, a newer card with active maker support is worth the difference.
The other thing worth knowing before buying is that ConnectX-3 predates some conveniences people assume are universal, and the firmware on OEM-branded cards varies. If you buy a Dell or HPE branded card and it refuses a third-party transceiver, that is a known behaviour rather than a faulty card, and it is the usual reason people reach for the crossflashing guides.
The mlx4 driver ships in the mainline Linux kernel, which is what actually determines whether your system recognises the card - so TrueNAS, Proxmox, Unraid and ordinary Linux distributions see it without you installing anything. 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.
ConnectX-3 has reached end-of-life at NVIDIA. That means no new firmware or driver work from the maker. It does not mean the card has stopped working, and it does not mean your operating system has dropped it. 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.
ConnectX-3 cards were sold in enormous volume to server makers, so Dell, HPE, IBM and Lenovo branded versions are everywhere and are usually cheaper than the Mellanox-branded equivalent. Some OEM firmware behaves differently with third-party modules. There is long-established community practice for reflashing these to generic Mellanox firmware; we link the maintained guides rather than restating the steps, because getting it wrong bricks the card.
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 an SFP+ 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 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.
It depends entirely on your time horizon. It is end-of-life at NVIDIA, so no new firmware or drivers are coming. But the mlx4 driver is in the mainline Linux kernel and in-kernel drivers are removed slowly and with notice, so the card works today and will keep working for the foreseeable future. Sound for a machine you will rebuild in a few years; a gamble for something you want to leave untouched for a decade.
Port count. The MCX311A family is single-port SFP+ and the MCX312A family is dual-port. For a point-to-point link between two machines you only need one port per machine, so the single-port card is usually the cheaper and entirely sufficient choice.
Generally yes, and they are usually cheaper. The catch is firmware: some OEM cards are pickier about which transceivers they accept. If you hit that, the established community practice is to reflash to generic Mellanox firmware, and there are maintained guides for it. We link those rather than reproducing the steps, because a mistake there bricks the card.
mlx4, which ships in the mainline kernel. That covers TrueNAS, Proxmox, Unraid and standard Linux distributions without installing anything. Windows support for a card this old is worth checking against NVIDIA's current driver page for your specific part number before you buy.
These are PCIe cards and both full-height and low-profile brackets exist, but the bracket fitted is not always the one you need and a spare is not always in the box. Check what your case requires before ordering, because a bracket mismatch is the most common reason a cheap card sits in a drawer.
For a direct link the two ends have to agree on a speed both support, and mixing generations is where that gets fiddly. Two of the same card is the simple answer for a point-to-point build. If you are connecting to a switch, the switch negotiates each port separately and the question does not arise in the same way.
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.