While performing some testing a few weeks back, I needed to enable jumbo frames on one of our Fujitsu 250s. This was accomplished with the following three steps:
1. Add the following line to /etc/system:
$ echo "set fjgi:fjgi_jumbo=1" >> /etc/systemd
2. If the default 9000 byte MTU isn’t ideal, add the preferred MTU to
the /etc/fjmtu.fjgiX file
$ echo "8192" >> /etc/fjmtu.fjgi0
3. Reboot the system.
If everything works correctly, ifconfig will report the larger mtu.