QSFP28 vs QSFP+ direct attach cables

[abq]

I have read the FS Community's excellent article, "SFP vs SFP+ vs SFP28 vs QSFP+ vs QSFP28, What Are the Differences?", at link Things you should know about SFP, SFP+, SFP28, QSFP+ and QSFP28 Transceivers.

Does any have any experience with using QSFP28 breakout cables (100gb>4x25gb) with the Mellanox SX series switches (esp SX6012)? Or the Brocade ICX series switches (esp ICX7450)? ...Looks like the '28' stuff is just an upgrade to '+' stuff, with full backward 100gb/25gb cable compatibility with the 40gb/10gb ports & cards.

I wanted to confirm with someone who has experience with 'QSFP28/SFP28' type cables in Mellanox & Brocade equipment (switches & cards), before I spend some real money (DAC type).

Thank You

 

[abq]

I am purchasing a couple 1 meter Dell QSFP+ to 4xSFP+ cables for $13 each, and couple QSFP28 to 4xSFP28 cables too. I will see how they work out with my Brocade & Mellanox equipment.

 

[Wolfcastle]

Did the cables end up working? I have an oddball situation where I have an ICX 7450 and have access to a few 100G QSFP28 LR4 transceivers but no 40G QSFP+ transceivers. I think it could possibly work but will likely be a completely unsupported mode. I'll find out soon enough, I guess.

 

[Freebsd1976]

Did the cables end up working? I have an oddball situation where I have an ICX 7450 and have access to a few 100G QSFP28 LR4 transceivers but no 40G QSFP+ transceivers. I think it could possibly work but will likely be a completely unsupported mode. I'll find out soon enough, I guess.

Use mellanox qsfp28 to sfp28 on sx6012 , run smoothly
Also finisar qsfp to 4 sfp aoc 7m work on sx6012
But one Amphenol qsfp28 to 4 sfp28 1m dac only two sfp28 can work, the other report crc error with sx6012 port red led

 

[Spartus]

I have a mix of 56G and 100G equipment
connectx3 & 4 VPI cards
My only switch is a SX6036

the mellanox 100G DAC cables work on the switch.

KAIAM QSFP28 100G XQX5004 are detected by the switch, but don't seem to work. I have no idea why but in documentation for other optics I see mentions of retimers for slower speeds, so many these don't have them (I can't find documentation).

I'm now trying to decide if there are other 100G cables I want to invest in as a slowly migrate to 100G but haven't done the switch yet, or do I buy a cheap batch of 56G cables.

My biggest obstacle is the SX6036 can run infiniband and ethernet simultaneously, but I don't know any 100G equipment that can do this...

 

[Wolfcastle]

I believe that QSFP28 and QSFP+ (QSFP14) are identical apart from the added bandwidth in the QSFP28s. My understanding is that these cables are totally passive so the only difference is whether someone checks that they can handle 28GBaud vs 14GBaud. I would be willing to bet that some of the newer QSFP+ passive cables are probably good for QSFP28 operation.

As for my test, it did not end up working, I wasn't able to get a connection between my ICX7450 and my Mellanox ConnectX-3 card using the 100G LR4 QSFP plugs, sadly.

 

[NablaSquaredG]

My biggest obstacle is the SX6036 can run infiniband and ethernet simultaneously, but I don't know any 100G equipment that can do this...

As far as I know, there are no VPI switches above 56G (sadly...)

Although RoCE v2 is pretty competitive at 100G

 

[arnbju]

My fs.com QSFP28 DAC Cables was not detected by early software versions on SX6012. With version 3.6.8010 they work without issue at 56Gb/s.

 

[NablaSquaredG]

My fs.com QSFP28 DAC Cables was not detected by early software versions on SX6012. With version 3.6.8010 they work without issue at 56Gb/s.

But only 56G Ethernet I suppose, Infiniband should be limited to 40G FDR10

 

[arnbju]

I have only tried Ethernet, don't know about Infiniband.