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.
9014 between Windows and FreeBSD works just fine. As I recall, on Windows, the jumbo frame sizes are in a dropdown.
For fun, I did just now try 9000 for Fedora <-> FreeBSD and it doesn’t work either. Running ifconfig periodically, I see the interface going up and down with the correct IP address and MTU size for a moment, then back to no address. Switch things back to 1500, everything works fine.
What’s odd is that, on some rare occasions, after playing around changing things (interface up/down, changing MTUs, whatever), I’ll get things to work at a higher MTU. But, as soon as I reboot, no luck.
The Fedora 28 upgrade with a newer kernel fixed this, so presumably something was fixed in a later kernel.
And, certainly, I don’t need jumbo frames, but if you’re doing large transfers over 10GbE (which I’m doing), jumbo frames will easily give you another 25-50% bandwidth over non-jumbo frames (depending upon application/protocol).
Unfortunately, that user has been banned for 1000 years and cannot offer a rebuttal to your statement. However, could you please provide evidence of the performance with NFS with/without jumbo-frames for a comparison? Thanks.