Update
After a couple of days, 1g autoneg between my x520 and the CSS610 stopped sorting out a connection. Had to force the card to 1g to get it linking again.
Mellanox Connect-X 3 card arrived. Same test platform, same fibre, same Intel E10GSFPSR optics = immediate 10g auto negotiated link.
FWIW: optics I’ve tested successfully so far (with the Mellanox card, Intel x520 is failure city with the CSS610).
- Intel E10GSFPSR
- Mellanox MFM1T02A-SR
(these are both Finisar manufactured at a guess) - FS.com NETGEAR AGM731F Compatible 1000BASE-SX SFP
- FS.com 1m 10G SFP+ Passive Direct Attach Copper Twinax Cable
I’ve scored some cheap genuine Finisar FTLX8571D3BCL off local ebay for more testing with once post sorts itself out and delivers them.