"failed to load because an unsupported SFP+ module type was detected" problems with ixgbe driver under RHEL

Issue

• We experience a problem with the ixgbe driver with the Intel Corporation 82599EB 10-Gigabit SFI/SFP+ (Small Form-factor Pluggable transceiver). When trying to load the ixgbe module, it often fails:

# grep ixgbe /var/log/messages

Nov 19 11:07:03 hostname kernel: ixgbe 0000:0e:00.1: MAC: 2, PHY: 1, PBA No: G18786-002
Nov 19 11:07:03 hostname kernel: ixgbe 0000:0e:00.1: Intel(R) 10 Gigabit Network Connection
Nov 19 11:07:03 hostname kernel: ixgbe 0000:0f:00.0: PCI INT A -> GSI 40 (level, low) -> IRQ 40
Nov 19 11:07:03 hostname kernel: ixgbe 0000:0f:00.0: failed to load because an unsupported SFP+ module type was detected.
Nov 19 11:07:03 hostname kernel: ixgbe 0000:0f:00.1: PCI INT B disabled
Nov 19 11:07:03 hostname kernel: ixgbe 0000:0e:00.0: p6p1: NIC Link is Up 10 Gbps, Flow Control: RX/TX

• What is the performance impact of using an unsupported spf via editing modprobe?

• How to know which SPF modules are supported by the server and operating system?