is it possible to configure "duplex auto" and speed auto" on an interface where a SFP module is inserted?
E.g. on an IE-3000-8TC with GLC-FE-100FX-RGD or Cisco WS-C3750G-12S with GLC-GE-100FX?
Thank you very much for your answer.
I do not believe that you can change the transmission speed on the SFPs you're using. Their types clearly show that they are built for a particular variant of fiber Ethernet, namely, 100FX. As opposed to metallic Ethernet where a NIC can speak all standardized speeds from 10Mbps up to its maximum supported speed (e.g. a GigE NIC speaks 10, 100, and 1000Mbps), an optical Ethernet module usually support only the specific transmission speed for which it was constructed, and no other. The reason is fairly simple: different variants of optical Ethernet usually use different wavelengths, necessitating different hardware in SFPs.
So the lack of the speed command is natural.