SFP give us freedom of choice and granular control over the media being used in the network segment. Mix and match optic fibre and copper of various throughputs and lengths of the segment. Very convenient and flexible solution and easily replaceable SFP modules. 

When troubleshooting issues or during maintenance, the hardware details of the SFP module plugged into a host NIC may need to be identified and verified. Typically the useful information is printed on the SFP label but who has the time for this. More importantly, it would mean taking the SFP module out and that means another maintenance window.

Using ethtool on AHV and XenServer will help with retrieving information like vendor, model, part number, serial number, transceiver type, cable length, connector type, signal quality, and more.

For more details refer to KB-9102 How to identify plugged-in SFP module model, manufacturer, and hardware details