Solved: Configure duplex and speed auto on SFP port

Kyle Lenderlof · ‎09-02-2014

Hello,

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.

Kind regards

Kyle

Peter Paluch · ‎09-03-2014

Kyle,

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.

Best regards,
Peter

View solution in original post

vinalsha · ‎09-03-2014

Yes. We can.

Kyle Lenderlof · ‎09-03-2014

Ohhh okay thanks.

What I am doing wrong here:

IE-3000-8TC with IES-LANBASEK9-M Version 15.2(1)EY

interface GigabitEthernet1/2
description trunk
switchport mode trunk
media-type sfp
!

Switch(config)#int gi1/2
Switch(config-if)#speed ?
% Unrecognized command
Switch(config-if)#duplex ?
full Force full duplex operation
half Force half-duplex operation

Thank you.

Peter Paluch · ‎09-03-2014

Kyle,

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.

Best regards,
Peter

vinalsha · ‎09-03-2014

Hi Peter,

You are right.

I am using SFP like: QSFP40G-4SFP10G

With this SFP I have the option to configure different speeds and speed auto.

switch(config-if)# speed ?
10 10Mb/s
100 100Mb/s
1000 1Gb/s
10000 10Gb/s
40000 40Gb/s
auto Auto negotiate speed

Depending on type of SFP, we can or we cannot configure "speed auto".