Hello there.
I have 2 CRS326-24G-25 + RM and 2 S + RJ10 products. I have one SuperMicro X540-AT2 10 10g card. I have a Slackware based diskless server. When I connect 10gb with sfp, client computers do not boot without disk. When I plug the cable into the 1 gb port, the computers turn on without any problem. (I had a dell x540 card before and it was running at 10 gb)
Where does booting stop? After kernel is already loaded and driver (re-)initializes NIC? Intel implemented a SFP whitelisting and linux driver (seemingly contributed by Intel) checks that. This is governed by certain bit in card’s ROM and not all vendors set it. It is possible to instruct driver not to check SFP compatibility by passing aporopriate option to kernel/driver. You can read more about it in several articles, one is this one.
Another possibility is that SFP is genuinely not compatible with NIC chip … but it would fail with all NICs using same chipset.
tftp also stays. gives a timeout error. I updated the firmware of the ethernet card. I’ll look at the other points you mentioned.