Description
The Mellanox ConnectX-4 Lx EN is a dual port 25 gigabit Ethernet network interface card using SFP28 cages on a PCIe 3.0 x8 interface. It is a data center and enthusiast home lab component rather than a consumer product, and the listing contains almost no information beyond what is in the product title.
Buyers looking for a consumer network upgrade are in the wrong place here and should consider the TP-Link Archer TX3000E for wireless or the EDUP AX3000M USB adapter for a simpler option. This card belongs in a server, a workstation or a home lab with switching to match.
What 25GbE On SFP28 Actually Requires
The specification in the title is the whole product description, so it is worth unpacking what it commits a buyer to.
SFP28 is a cage, not a cable. The card has two empty ports and something has to go into them: either a direct attach copper cable, which is a fixed length cable with the transceiver moulded onto both ends and is the lower cost option for short runs within a rack, or an optical transceiver module plus fiber, which costs more and covers longer distances. Neither is included, and neither is mentioned on this listing. Budgeting for the card alone will not produce a working link.
The other end also has to exist. A 25 gigabit link needs a switch with 25 gigabit SFP28 ports, or a second card in another machine for a direct point to point connection between two systems. That second option is the common home lab approach and works well, connecting a workstation directly to a storage server without a switch in between.
PCIe 3.0 x8 is the host interface. Eight lanes of PCIe 3.0 provide roughly enough bandwidth for both ports running at full speed simultaneously, but the slot it goes into must actually be wired for eight lanes. Many consumer motherboards have physical x16 slots wired electrically at x4 or x1 for the secondary positions, and a card in one of those will be bandwidth limited. Checking the slot layout of the target board is essential, and that layout is exactly the specification most motherboard listings in this catalog omit.
The Tall Bracket
The product title specifies a tall bracket, which means a full height mounting bracket rather than a low profile one. That fits a standard tower, workstation or full height rackmount chassis. It does not fit a 1U or 2U server designed for low profile cards, or a small form factor desktop.
Low profile brackets are typically available separately and are often included in the retail box, but this listing does not state whether one is supplied. Anyone installing into a slim chassis should confirm before ordering.
What The Listing Does Not Provide
The gap here is unusually wide even by the standards of this catalog. The description field consists of a single generated sentence that simply restates the title with the phrase crafted with care inserted into it. The feature bullets array is completely empty. Not one bullet.
Consequently there is no specific part number, and ConnectX-4 Lx is a family with several distinct SKUs that differ in port speed, port count and firmware. There is no supported operating system list, which matters because driver availability across Linux distributions, Windows Server and VMware is the first thing a buyer in this category checks. There is no statement of supported features such as RDMA over Converged Ethernet, SR-IOV, hardware offloads or PXE boot, all of which are the reasons anyone chooses a Mellanox card over a cheaper alternative. There is no power consumption figure, no operating temperature range and no warranty term.
Most tellingly, there is no customer rating and no review count on the record at all. There is no peer signal to fall back on.
Highlights
- Dual port 25 gigabit Ethernet with SFP28 cages.
- PCIe 3.0 x8 host interface.
- Tall, full height mounting bracket.
- Listed weight of 1 pound.
- Manufacturer given as Mellanox Technologies.
That short list is the complete set of facts the listing supplies.
Things To Consider
One practical point about cooling. Enterprise network cards of this class are designed for server chassis with strong front to back airflow, and many of them use a passive heatsink that assumes that airflow exists. Dropped into a quiet desktop tower with gentle case fans, a 25 gigabit adapter under sustained load can run hot. Anyone installing this into a normal PC case should make sure there is airflow across the expansion slot area rather than assuming the card cools itself.
Age is a genuine factor. The listing gives a first availability date of July 2, 2016, which makes this one of the older products in the catalog. Enterprise networking hardware has a long service life and ConnectX-4 Lx cards remain widely deployed, but a buyer should understand they are purchasing a design approaching a decade old, and should check current driver support for their operating system before committing.
The buying advice for a component like this is straightforward: work from Mellanox documentation and from the specific part number, not from this listing. Ask the seller for the exact SKU printed on the card, then look up that number. A ConnectX-4 Lx sold without a part number could be any of several variants.
The dimensions listed as 8.7 by 6.8 by 2.1 inches describe the packaging rather than the card. Buyers assembling a fast local network around this card should also plan the storage on the other end, and options are covered in the devices category and the enclosures category, including the Asustor AS5402T.
Who It Suits
This card suits a home lab builder, a small studio or an engineer who needs a fast point to point link between two machines, or who is adding 25 gigabit connectivity to a server that already has matching switching. For anyone moving very large files between a workstation and storage, a direct 25 gigabit connection between two cards is a well established and cost effective approach.
It is the wrong purchase for a consumer PC, for anyone without SFP28 switching or a second card, for buyers who have not budgeted for transceivers or direct attach cables, and for anyone installing into a low profile chassis. It is also difficult to recommend from this listing specifically, because the listing does not identify which variant of the card is being sold.
