SFP+ DAC Cables - Live Prices by Length

Passive SFP+ direct-attach cables by length

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.

Active optical cables - when the run is too long for copper

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.

What a DAC actually is

A direct-attach copper cable is a twinaxial cable with the transceiver housings moulded permanently onto both ends. It is not a cable plus two modules that you assemble - it arrives as one object and it leaves as one object, and the ends cannot be separated from the middle.

That construction is the whole of its advantage. Because the ends are fixed to the cable at the factory, there is no module to buy, no module to match, and no module to be rejected for identifying as the wrong thing. It is the cheapest way to connect two SFP+ ports by a wide margin, and the tables above show that margin plainly against the module prices.

Passive is the variant you almost certainly want. A passive DAC contains no active electronics - it is a controlled-impedance copper cable with connectors, and it draws essentially nothing from either port. Active DAC exists, contains signal conditioning circuitry, costs more, and buys reach that most people do not need. Everything in our table is passive.

The trade you accept is inflexibility. The length is decided at purchase. If you buy two metres and need three, you buy another cable - there is no extending it, no joining two, and no swapping just the end.

The passive reach ceiling

Passive direct-attach copper does not run far. The practical ceiling sits around seven metres, which is where the longest cables in our catalogue also sit - and that is not a coincidence, because the market stops making longer passive cables at roughly the point the signalling stops being reliable.

This is a specification limit rather than a quality one. A longer passive cable is not a worse cable; it is a cable that would not meet the standard, so reputable makers do not sell one. If you find a passive SFP+ cable advertised well beyond that range, treat the listing with suspicion rather than as a bargain.

Seven metres covers more situations than people expect - two machines in one room, a rack and a desk, a NAS in a cupboard and a workstation on the other side of the wall. Measure the route the cable will actually take rather than the straight line, because cables go around furniture, up walls and through management channels, and the honest figure is usually half again what the tape measure suggested.

Past that ceiling, an active optical cable is the next step. It looks like a DAC - a sealed object with fixed ends - but carries the signal optically and reaches far further. It costs more, and the tables above let you see exactly how much more today.

Compatibility, stated carefully

DAC cables are often described as having no compatibility drama, and that is nearly true but not quite, so it is worth stating precisely.

A DAC's moulded ends still identify themselves to the ports they are plugged into, in the same way a separate module does. A switch that enforces vendor coding can in principle refuse a DAC on the same basis it refuses a module. In practice this is reported far less often than with optical modules, and the cheaper end of the market sells cables labelled as compatible with named vendors for exactly this reason.

So the accurate framing is not that DACs cannot be rejected - it is that they are rejected much less often, and that for a link between two machines you own, both of whose cards you chose, the question effectively does not arise. Where a seller has listed compatibility claims for a cable, our table shows them badged, the same as everywhere else on this site.

The other practical note is thickness. Twinax is stiff, and it gets stiffer as it gets longer and lower gauge. A seven-metre DAC is a substantial physical object with a real bend radius, and routing it through tight cable management is not always the job the diagram suggested.

Choosing a length

Measure the route, not the distance. Then add margin - a cable pulled taut across its full length is a cable that will be unplugged by the first person who moves the machine.

Buying slightly long is cheap insurance. The price difference between adjacent lengths in the table above is generally small next to the cost of buying a second cable because the first one did not reach, and unlike a fibre patch lead there is no option to swap the ends onto a longer run later.

Where two lengths are close in price, take the longer one. Where the price jumps sharply - which it does at the top of the passive range, because the engineering gets harder - that is the point to check whether the run genuinely needs to be that long or whether the machines can move closer.

And if the answer is that the run is longer than passive copper can serve, the AOC table above is the honest next step rather than a longer passive cable that the standard does not support.

Where to go next

The two-machine build prices one of these plus two cards · DAC versus fibre is the length-and-cost decision in detail · transceivers covers what you need instead when copper cannot reach · the 10GbE hub has the cards.

Frequently asked questions

Sources

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.

1. NVIDIA (Mellanox) - ConnectX-3 EN product line and lifecycle status (nvidia.com, 2026)
   Used for: that ConnectX-3 has reached end-of-life status with NVIDIA, and the MCX311A / MCX312A / MCX314A part-number family. EOL means no new firmware or driver work from the maker; it does not mean the card stops working, and the page says so in those terms.
2. The Linux kernel project - mlx4, mlx5, ixgbe and i40e in-tree Ethernet drivers (kernel.org, 2026)
   Used for: that mlx4 (ConnectX-3), mlx5 (ConnectX-4 and later), ixgbe (Intel 82599/X520, X540, X550) and i40e (X710) ship in the mainline Linux kernel. This is why an end-of-life card can still be a sane purchase, and it is a documented fact rather than a forum claim.
3. DatacenterDisk - Live catalogue - NIC, DAC and transceiver listings (datacenterdisk.com, 2026-08-11)
   Used for: every price on this page, read from our catalogue at request time. Seeded 11 August 2026: 24 network cards across 6 models, 24 DAC cables, 8 transceivers. Every card is split tier 1 (the listing is that part) or tier 2 (a third-party board asserting that silicon).
4. DatacenterDisk - Sourcing note - power figures and compatibility claims (datacenterdisk.com, 2026-08-11)
   Used for: We publish no per-port wattage for either cabling path. The relationship - 10GBASE-T draws more power and runs hotter than SFP+ direct attach - is documented at product level and is stated here. The magnitude is not, because we have not fetched and logged a source we can cite for it. Separately: every 'compatible with' phrase shown on this site is stored as a seller claim at tier 2 and badged wherever it renders. We have not tested any module against any switch.