How to connect QSFP28 to 10GBase-T? Transceivers or Breakout cables?

[TonyA]

I just managed to pick up a HP 3032Q Switch for a great price and am intending to run Sonic on it with Mellanox 100Gb cards and 100Gb DAC cables (it's only going to be for 5 machines max).

I notice there's no SFP or SFP+ ports on the switch and short of running some kind of PC based bridge is there a cheapish way to get a 10GBase-T connection to connect to the rest on my network?

From what I've read I don't think there's any QSFP28 10GBase-T transceiver adapters, so think I might have to go breakout cable then transceiver adapter, which is a bit ugly and might work out stupidly expensive relatively, so may just setup a bridge on one of my PCs.

Thoughts/Ideas?

 

[nexox]

There's an adapter from QSFP28 to SFP28 called the QSA28, if you only need 10G the the QSFP to SFP+ adapter will be fine, that's just called a QSA, costs about half as much, under $20 on ebay, and then you fit a regular SFP+ 10GBaseT transceiver into it.

 

[sko]

QSFP28 is 4x25Gbit, so you can only make it SFP28, i.e. 25GBit by using a single lane, but not 10GBit. For that you'd need a transceiver that can negotiate on 10Gbit but still reports 25Gbit to the switch - not sure if those actually exist, I only ever seen those for 10->1Gbit workarounds. For copper this might be even harder to find or simply doesn't exist...

 

[nexox]

Almost all SFP28 ports are backwards compatible with SFP+ and probably even plain 1G SFP, you can pretty certainly use a single 10G SFP+ module in a QSFP28 port with an adapter, unless your switch is really unpleasant.

 

[NablaSquaredG]

QSFP28 is 4x25Gbit, so you can only make it SFP28, i.e. 25GBit by using a single lane, but not 10GBit. For that you'd need a transceiver that can negotiate on 10Gbit but still reports 25Gbit to the switch - not sure if those actually exist, I only ever seen those for 10->1Gbit workarounds. For copper this might be even harder to find or simply doesn't exist...

That is wrong.

Almost all SFP28 ports are backwards compatible with SFP+ and probably even plain 1G SFP, you can pretty certainly use a single 10G SFP+ module in a QSFP28 port with an adapter, unless your switch is really unpleasant.

That is correct.