I’ve upgraded my network connection from my workstation to my FreeBSD NAS. Both sides have an Intel X550-T2 (copper, 10 GbE) interface connected by a simple Cat6a cable between them (no switch). These cards support 9014 byte jumbo frames. Statically (obviously) assigned IPv4 (only) addresses on each side.
With Windows on my workstation and FreeBSD 11 on the NAS side, 9014 byte frames work perfectly. With Fedora Linux 27 on my workstation (latest, all updates), 9014 byte jumbo frames cause the card to just repeatedly try to connect to the remote side with no success. No pings, nothing. If I switch the MTU to 1500 bytes on the Linux side, no problem. As soon as I pick anything besides 1500 bytes, badness. Put it back to 1500 bytes, success. This is all very repeatable.
I’ve never seen anything like this.
Anyone have any ideas to troubleshoot?