100BaseFX-FE SFP Full Duplex in 3560-POE-8 Switch?

Unanswered Question
Apr 29th, 2009

Is there a way to set a 100FX-FE SFP module installed in a 3560-POE-8 Switch to operate in full duplex mode. It is autonegotiating to half duplex and will not accept the "duplex full" command under the GigabitEthernet0/1 interface configuration.

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Overall Rating: 5 (1 ratings)
Giuseppe Larosa Sat, 05/02/2009 - 03:31

Hello Jim,

this is probably an issue that you can solve with an IOS image upgrade or simply specifying to use the SFP.

A fiber based SFP should be always full duplex.

However, 100FX-FE SFP may require a newer image.

Another aspect of the issue is that you may need to specify that you want to use the SFP if the port has both an RJ-45 and a SFP slot it may defaults to RJ-45.

int gi0/1

media-type sfp

you may be seeing the results of autonegotiation on the RJ-45 port where half-duplex is possible.

Hope to help


NPT_2 Mon, 05/04/2009 - 07:57

Thanks for the advice. Once I applied the media-type sfp command I was able to apply the duplex full command to the interface. Before then the fiber link would only link in at half duplex. Thanks for the help.

Giuseppe Larosa Mon, 05/04/2009 - 10:11

Hello Jim,

nice to hear it solved.

However, when media-type is set to rj-45 the switch doesn't use the fiber but should try to used the rj-45 cable.

setting to media-type sfp opens to you the commands appropriate for a fiber based port.

Hope to help


NPT_2 Mon, 05/04/2009 - 10:17

I guess the default must be auto as other than the duplex issue my fiber link was fully functional and I had full connectivity to clients on that switch (and the switch itself).

Giuseppe Larosa Mon, 05/04/2009 - 10:21

Hello Jim,

my experience with routers like C7200 with NPE-G1 was different the command was necessary to start to have a working fiber based link.

Hope to help



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