25G SFP28 capable of rate-adaption down to 1G?

Mon Jan 31 18:42:48 UTC 2022

Hi Bill,

I did that a few months ago with SFP+. Purchased few with copper (different vendors), few with fiber (from Solid Optics, they provide a very nice USB interface to configure them if needed), and used them at different speeds, depending on the equipment on both sides.

The copper ones also work at 2.5 and 5 Gbit/s,  not sure 

For example, an old 1 Gbit/s SFP-only switch works fine connecting it to a newer switch that has SFP+ (10 Gbit/s). Of course, the speed goes down to 1 Gbit/s only. In this specific case, just for fun, I tried both copper and optical, and both worked.

Some DAC and AOC also work the same as I know.

Note that it may depend on the specific vendor/model, and some of them you may need to "program" them to support multispeed or a fixed speed.

SFP28 is just an enhanced SFP+, an in fact SFP28 work in SFP+ interfaces. So it should be the same, as the electrical signals are the same.

Regards,
Jordi
@jordipalet

El 31/1/22 19:07, "NANOG en nombre de Bill Woodcock" <nanog-bounces+jordi.palet=consulintel.es at nanog.org en nombre de woody at pch.net> escribió:

    Hey, does anyone know of an SFP28 capable of rate-adapting down from 25G on the cage side down to 1G on the line side?  Can be copper or fiber on the line side, I don’t care, my interest is in the chip inside.

    Thanks,

                                    -Bill

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