Customer is having problem with igb driver that it does not recognize sfpt-t fiber adapter module. It does recognize another copper module on the same system. (i.e. eth0 with copper works, eth1 with fiber does not work). The same fiber (as well as copper) adapter works with both igb-5.0.5 and igb-5.2.9.4 driver downloaded from intel.com. $ lspci -nn 01:00.1 Ethernet controller [0200]: Intel Corporation DH8900CC Series Gigabit Fiber Network Connection [8086:043a] (rev 21) There are lot of differences between wrl6 and igb-5.0.5 driver, so hard to compare. But some relevant differences I found were that – wrl6 driver is missing some essential routines for media (copper or fiber) check – igb_check_swap_media. CONNSW register is not as much used in our driver which is Copper/Fiber Switch Control Register 0x0034. There are lots of other diffs also. I back ported just this “media check code” from intel-5.0.5 driver to wrl6 driver, but it did not fix the problem. There may be something more to it. Customer wants any supported solution from WR, so that working igb driver can be configured both ways - either built-in or as a loadable module.