based on my previous question about GPON networking: Let’s assume I can find a config which actually works for GPON networking. The major problem is: while the GPON SFP module would only have a 1gbe speed (max), it takes one of the 10gbe NICs (and I’d need both). So, what options do I have if I need a SFP cage for GPON networking and 2 10gbe ports? or would the advice be “bury your GPON SFP project, keep the external ethernet->GPON bridge and accept the additional SPOF”?
For 1 gbps you could use an USB - sfp converter
https://a.aliexpress.com/_EvxjKGk
Hopefully it has a linux driver in mainline… It says it is linux supported.
Or maybe an rj45 to sfp converter like so:
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thank you Eric!
this would indeed solve the issue …
time to make a list of everything I need then …
hopefully it won’t take too long anymore before the R4 pro is available on aliexpress, as I can only pay in €, not $ 
I think the main difference between the 2 options (usb-sfp or rj45-sfp) is hardware flow offloading. Via usb it cannot be offloaded in hardware. Although at only 1gbps it may not really be a problem for this cpu. Software flow offloading could still be enabled.
… but if using RJ45-SFP bridge it won’t be manageable, right? Though I have my doubts whether there is anything manageable in the SFP module at all, USB->SFP may still expose some mgmt capabilities
EDIT and it (hopefully) can tell me whether the module is in trouble or not … if using RJ45->SFP there’s no chance
Maybe you can poll it over telnet…
concerning supported: according to manufacturer it has a realtek RTL8153B or RTL8213 chip … I’ll check the USB drivers ID of realtek, guess I can find it in there
do you think those modules have a separate internal IP to poll?
Never used one before, time to read up in the topic. Some of these things even run openwrt.
alternative solution: mpcie modules with 2x 2.5gbe do exist (I even got one). is this also the case for 10gbe? and would it be feasible or a horror solution for the 3.3V line?
The bottleneck would be the single lane PCIe, as the second lane is not at standard pins, even if the 3.3V would hold.
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all right, I didn’t think of that one, but good point indeed! What would introduce the highest latency? I mean, the USB bus might introduce extra latency I do not want for all devices in my home. on the other side, converting RJ45 to SFP and back may even be worse
this may also combine everything @ericwoud : https://www.lr-link.com/products/LRES2204PF-SFP.html What do you think? Worth a shot? I thought pcie would hardly require some latency … or am I wrong?
This one is only 1gbps…
yes, so I can host the WAN GPON SFP in there, no?
Should be ok theocratically, if the soc plays nice with this chip and you include the driver in the kernel.
You cannot set up hardware flow offloading on it, but at 1gbps I guess it is not a big deal
Cool! I’ll try it when I can get my hands on a R4 pro. Topic closed then!