2960G won't establish link via SFP

[eekman]

At home I got a single mode fibre cable coming in, connecting me to the internet. It's currently connected to a PacketFront switch, installed before I moved in. It works fine but has a 100 Mbps limit, so I want to change it.

I talked to the ISP and they even sent out a guy to my house. He confirmed the fibre type, wavelength and speed at the other end. Since I own that PacketFront switch I can do whatever I want with it. Great, I have a 2960G spare. Lets use that for now.The alternative is to pay a ridiculous amount of money for a weird-branded non-managable switch provided by the ISP.

I put a single mode Cisco 1-Gbit LX SFP in the 2960G and connected the fibre cable. No link. Nothing in the log. No nothing. It's down/down. I tried switch place on the LC connectors - same thing. Tried shutdown/no shut and "the usual t-shooting stuff" - no change. The very service-minded ISP guy gave me a Waystream LX SFP, thats what they use, and we tried that. But no link, and the switch complains about unknown transceivers and bad CRC, although I configured the switch with service unsupported-transceiver and turned off err-disabling for unsupported gbics. We tried the same Waystream SFP in the switch he brought along, and it worked fine right away.

I also tried a HP SFP, and that behaved exactly like the Waystream SFP. 

I tried two different 2960G, one with 15.0 software and one with 12.2. They behave exactly the same way - no link at all.

I'm out of ideas, do you guys have any suggestions? When you use an unsupported SFP, should the speed and type show up in "show int status"? For me it does not, it just says "unkown". 

[Georg Pauwen]

Hello,

use the compatibility matrix linked below to check what SFPs your 2960G supports, and what the minimum required software is...

https://tmgmatrix.cisco.com/

[Mark Malone]

Hi
not all unsupported transceivers are supported , i know IBM are but using the command is not a guarantee for unsupported to work , its 50/50 whether they come up

is it single mode fiber or MMF , if MMF use GLC-SX-MMD there cheap 1GB MMF
also make sure the fiber is crossed , light from sfp goes into port with no light on switchside , rx and tx are opposite or it wont come up at layer 1

[eekman]

It is SM. It is confirmed by ISO and it works with their SM-SFP in their switch.

The first SFP i tried is found and accepted by the switch, but will not link Up anyway. The other ones is unsupported. So probably two different issues there. I tried switching the individual connectors, it made no difference.

[Mark Malone]

theres only a few SMF SFPS as its a layer 2 switch and there expensive , much more than MMF unfortunately due to the distance they can do
here they are below

https://tmgmatrix.cisco.com/?si=2960g

[Leo Laohoo]

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@eekman wrote:

It works fine but has a 100 Mbps limit, so I want to change it.

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You need an optical module that support 100BaseFx.  

You tried using 1Gbps SFP which is not compatible. 

[eekman]

Thats is not it, the SFP works with in their switch.

[eekman]

The 100 Mbit limit is probably on the rj45 port in the packetfront switch. The fiber Link is 1000 in both ends.