Notes on using non-Intel SFP+ with Intel X520 DA2 on Linux.

• Add driver options

# cat << _EOF_ > /etc/modprobe.d/ixgbe.conf
options ixgbe allow_unsupported_sfp=1,1
_EOF_

• Unload and reload the driver

# modprobe -r ixgbe
# modprobe ixgbe

• Regenerate initramfs

# update-initramfs -u

Without this, allow_unsupported_sfp=1,1 will not be enabled on reboot.