> On Jan 31, 2022, at 8:02 PM, Randy Carpenter <[email protected]> wrote: > > > Are you talking about an SFP28 module that can link at 25Gb, but also 1Gb? > > We just put 1Gb SFPs in the SFP28 ports and they work fine. I have not seen a > single module that does both, but admittedly, I have not looked too hard, as > the 1Gb modules are so cheap. > > Or, are you talking about a module that presents as 25Gb to the switch, but > 1Gb to the client device?
The latter.
I remember there were two kinds of copper SFPs: cheap ones, which would talk 1G
on both sides, and expensive ones which would talk 1G on the switch/router
side, and 10M/100M/1G on the client side.
There seem to be similar kids of copper SFP+, though I haven’t actually tested
them:
https://www.discomp.eu/mikrotik-rj45-sfp-10-100-1000m-2-5g-5g-10g-metalicky-modul_d82667.html
https://datainterfaces.com/sfp-1000-rj45-10gbase-t-copper-sfp-transceiver-module-cisco-ready/
https://www.prolineoptions.com/dell-sfp-10g-t-de-pro-100-1000-10000base-tx-sfp-plus-transceiver-copper-30m
https://www.blackbox.be/en-be/i/14164/SFP+,10-Gbps,RJ-45/
https://www.bestbuy.ca/en-ca/product/startech-hp-jl563a-compatible-sfp-module-10-100-1000-10000-copper-transceiver-jl563a-st/14208481
Those seem like they might talk 10G on the switch/router side, and
10M/100M/1G/2.5G/5G/10G on the client side. Or it might be that they establish
whatever link speed they can on the client side, and then try to signal the
switch/router side to adapt to that rate; which seems possible but improbable.
Or it might be that they accept whatever speed the swich/router side tells them
it’s running at, and then only provide link at that rate on the client side;
again, possible but seems improbable. I haven’t actually taken any of these
into the lab to test them, anyway. And those are 10G on the switch/router
side, and I’m curious whether anybody knows of one that goes 25G/10G/1G on the
switch/router side, and 1G (specifically) on the client side.
I don’t actually want the SFP28, I just need to find a chip that does that in
the size/power budget of an SFP, and it seemed like the easiest way to do that
would be to find an SFP28 that did what I needed and bust it open to see what
chip they were using.
I’m sure you can guess why, given recent threads. :-)
-Bill
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