Is QSFP28 Backwards Compatible With QSFP+

Networking Networking Hardware
1

Hello,

My company currently has an old Arista switch which utilizes 6x QSFP+ ports at a max of 40 Gbps.

Switch: Arista 7050SX-72Q

I was tasked with building my company a new system, and I wanted to purchase a NIC to push higher rates (when we eventually replace the switch).

Initially I was planning on purchasing a Mellanox ConnectX-6, but the ConnectX-6 uses QSFP56 ports which I was told would not work with QSFP+ ports.

However, after some digging online I found that QSFP28 might be backwards compatible with QSFP+ (obviously capped at the upper rate of switch).

I plan on purchasing the following NIC : Mellanox ConnectX-5 Ex - MCX516A-CDAT

…as it uses QSFP28 ports, supports 100 Gbps, plus supports Windows 11 Pro for Workstations (the target OS for my company’s new system).

Does anyone know if it’s possible to connect the Mellanox NIC to my current switch and both pass and receive traffic to the switch?

Unfortunately, my company won’t be able to upgrade the switch for 1 to 2 years, and I’m stuck using the current switch.

However, I wasn’t able to find any NIC’s which worked with non-Server version of Windows operating at rates higher than 10 Gbps (as I tried NIC’s from Intel’s XL710 lineup (which a manufacturer confirms does not work with non-Server versions of Windows) as well as older Mellanox cards (ConnectX-3) with QSFP+ ports (which also does not support non-Server versions of Windows)).

Thank you,
Nelson

1 Like
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zwhere did you get that?
Nvidia says it does …
Screenshot 2022-02-25 at 09.04.06

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Hello MadMatt,

I couldn’t provide a link, but for Windows 11 (not Windows 10), I see the following:

image
image1320Ă—805 79 KB

That said, do you know if QSFP28 is backwards compatible with QSFP+?

Thank you,
Nelson

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Sorry, didn’t register Windows 11 … it is still a non entity to me … will have to retrain my brain :slight_smile:

It should be, but given the card is a 1Kplus item, the cables will be around 100 unless you can get a way of testing it on your hardware I would be very cautious …

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Hello MadMatt,

Understood.

Worst-case scenario, if it doesn’t work with my company’s switch, it’s only $1200.00 (the system it’s going into is $50,000.00) so it’s a small dent in the total cost.

The important thing is that it’s supported at the driver-level.

Thank you for your help,
Nelson

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Afaik Windows versions are well to a certain point backwards compatible and forwards compatible. So you can install Photoshop CS3 on a Windows 11 and you can install Creative Cloud on Vista. At some point things break BUT, drivers are the main focus point, so any Windows driver should work with any version. TNE.

Something compatible with Win11 makes it to most cases compatible with Win10.

The difference between them is just a reskin, default app versions (Explorer 11 on Win11) and a different scheduler.