Any difference between direct connect SFP+ Cable and switch connect SFP+

TheHaughom

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Oct 28, 2015
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Yes, you need a direct-connect cable/transceiver.
For the network card there is no difference though.
 

TheHaughom

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Oct 28, 2015
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DAC stands for Direct Access Cable.
Those are for connecting two computers/devices directly, and not through a switch.
 

pyro_

Active Member
Oct 4, 2013
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You can also use the DAC cables to connect a device to a switch rather than use optical tranceivers and fiber cables
 

nephri

Active Member
Sep 23, 2015
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Paris, France
If i understood correctly the question, is more than :
- Do we need to have a special transceivers for "cross" the data like we have on RJ45 or not ?
 

ekke

Member
Nov 16, 2015
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I'm also looking at 2x 671798-001 HP 10GB MELLANOX CONNECTX-2 PCIe 10GBe ETHERNET NIC as a point 2 point cpnnection between my workstation and freenas server, but I got almost 10m between them

Looks like I need to go the fiber router with 2x sfp+ like these
GENUINE HP 10GB SR SFP+ 455885-001 456096-001 455883-B21 Transceiver QTY 90 day

+ a suitable fiber cable.

maybe a 10m twinax DAC cable is compatible? like this one
37-1150-02 Cisco SFP-H10GB-ACU10M Twinax Network Cable 10M
 

nk215

Active Member
Oct 6, 2015
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There are direct connect cable that goes beyond 10M (25-30M), however they are very expensive as in $10/meter. At that price, it makes more sense to get a 2 SFP+ ports switch for the flexibility.
 

ekke

Member
Nov 16, 2015
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There are direct connect cable that goes beyond 10M (25-30M), however they are very expensive as in $10/meter. At that price, it makes more sense to get a 2 SFP+ ports switch for the flexibility.
It looks like the cheapest way is to get 2 sfp+ and 10M fiber

2x 10GBASE-SR SFP+ MMF 850nm Transceiver Module - 2x $16
1x 10 m LC-LC Duplex 10G OM4 50/125 Multimode Fiber Patch Cable $8.16

A switch with 2 ports for 10GBE would be great, but too expensive.

D-Link DGS-1510-20 16-Port Gigabit SmartPro Switch w/ 2x SFP Ports & 2x 10GBE
 
Last edited:

Rain

Active Member
May 13, 2013
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Alright, let's clear some things up.

First, DAC does not stand for "Direct Attach Cable," it stands for "Direct Attach Copper." DAC cables are generally used for inter-rack (not intra-rack) connections; for example, from top-of-rack switches to the machines located in that same rack. This is because name-brand DAC cables are generally cheaper than name-brand SFP+ transceivers.

Second, the data that goes into a DAC cable on one end is exactly the same when it comes out the other end -- they're not like crossover cables or anything like that. SFP+ transceivers and fiber will work just fine directly computer-to-computer without a switch. In fact, some manufacturers sell short, pre-made "active" optical cables meant for short runs instead of DAC cables just because optical cables are less bulky.

So, to answer the original question: The only difference is that DAC cables tend to be short. Other than that, no.

And, the follow up question: "Do we need to have a special transceivers for "cross" the data like we have on RJ45 or not?": No. DAC cables and SFP+ transceivers can both be used in connections from computer-to-computer without a switch.