Using a breakout cable with ConnectX-3 MCX354A

rahulkadukar

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Jun 9, 2020
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Can I use the cable linked below to connect my NIC to my router (Mikrotik CRS 326). The router only supports 10G so I will use only one of the SFP+ cables. Will this configuration work


OR

Should I get a QSFP+ to SFP+ module and then use SFP cable
 

klui

Active Member
Feb 3, 2019
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Connecting the denser end of breakout cables won't work on older cards like the CX3. Use a QSFP+ to SFP+ converter.
 

crdhn88

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Apr 11, 2020
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Last edited:

Rand__

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Mar 6, 2014
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No, 4:1 breakout will not work in NICs (except some fairly new HP cards which are special), only in switches.

The QSFP->SFP adapter will work fine.
Have not used it with transceivers, only DACs so can't comment on compatibility.
 
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kagurazakakotori

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Mar 5, 2017
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No, breakout cable is not supported on NICs, they only work on switches. Consider buying a QSFP to SFP adapter instead.
 

vangoose

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May 21, 2019
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No, 4:1 breakout will not work in NICs (except some fairly new HP cards which are special), only in switches.

The QSFP->SFP adapter will work fine.
Have not used it with transceivers, only DACs so can't comment on compatibility.

I have it with transceivers, it takes anything, FS, Broadcom, HP, Avago, anything I put int works.
 
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BeTeP

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Mar 23, 2019
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breakout cable is not supported on NICs, they only work on switches
40Gb/s to 4x10Gb/s mode is not supported by NICs. But 40Gb to 1x10Gb/s works just fine. This is exactly what the adapter does:
The RF (high speed data) channel of the SFP receptacle is connected to lane 1 of the QSFP+ connector. The
three remaining RF channels on the QSFP+ connector are not connected.
 
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deified

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Jun 11, 2020
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Can confirm [MCX354A-FCBT QSFP port1] --> [ MCP7F00-A01A (QSFP28 to SFP28)breakout cable] --> [Brocade ICX 10gb SFP+ port 1/3/1] this configuration does work. You get 1 of the 4 breakouts that will light up and connect. MAM1Q00A-QSA adapter is about 25 bucks and so is the breakout cable. Not sure if this will work for your specific hardware. But breakout cables do indeed work NIC(QSFP) to switch(sfp+)
 

chicken-of-the-cave

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Mar 13, 2020
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Mellanox's, regrettably, do not support breaking cables (there is a possibility that using a QSFP->SFP+ breakout cable on a Mellanox may work with one 10G lane, meaning one SFP+ cable would work, usually the first cable, but not all four).

That being said, certain Intel NICs do support breakout cables (specifically: X520-QDA1, XL710-QDA1, XL710-QDA2). Below is the links for the XL710 NICs (not sure what the procedure is X520) to change the QSFP configuration.