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Help with Sfp+ Fiber

Hey there,
I have a problem i can’t seem to get my head around.
I have a FreeNAS Server with a 2port 10GBit/s SFP+ Card (Chelsio T520-SO-CR)
I have 2 PCs with single port 10GBit/s Mellanox ConnectX Cards
All p2p between Server and PC. I used 2 Copper SFP+ twinax Cables up to now. Worked fine. I needed more distance so i got 2 Cisco FET-10G Fiber Modules and an LC-LC OM3 fiber cabel.

I can’t get a connection between 1 Mellanox Card and the Chelsio Card in the server. However i can get a connection between the 2 Mellanox card.

Do i need to have the same cards on both ends? Why doesn’t it work?
How can i troubleshoot it.

Thanks in advance. I’m a noob

I have had to unsnap and swap the orientation of the LC connectors on one end of a fiber jumper before in order to establish a link light. Usually the first thing I try when having trouble establishing a fiber connection.

Using all multimode transceivers and cable I assume?

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It’s probable that one of the cards doesn’t like that module. I have an Intel card that does not like one of my Mellanox modules, but will work fine over twinax.

Yes multimode whatever that means. And reversing the Polarity didn’t work.
But at least i know how to do it :smiley:

You seem to be right. FreeNAS outputs this when inserting a module:
cxl1: unknown port_type (9), mod_type (29)
cxl1: unknown transceiver inserted.

So it seems like i have to buy a 40€ Chelsio module to make it work. Quite a bit more expensive than the 10€ Cisco ones i got.

But i only need to have on module on the server side, right? The other one on the Mellanox side can be the current cisco one, right?

Transceiver module compatibility is all over the place. Technically, you should use officially supported ones, but often others will work. In my experience, it either works or doesn’t (never partially works, or is intermittent), but obviously I have only tried a small number of them., 10Gtek and Macroreer are good sources for cheap transceivers.

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The generic ones from will work with either if those cards.

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It is obvious that Cisco modules aren’t compatible with Mellanox Card(As far as I know, Chelsio Card has not a strict requirement on official modules).
So it is my recommendation that buying compatible modules provided by thrid parties due to the lower cost.
You can find many useful modules with good quality on 10Gtek.

@makodo watch out for how old a thread is before commenting on it. This one is over a year old. The issue has long since been resolved and in any case, you are merely restating what has already been said. OP had already identified that the Cisco modules were not compatible and I had already linked 10Gtek.