Mihaly Zachar wrote:

I have never used fibre connection yet. Now I got a server where the HW
(Dell R440) and the network connections are provided by others, my task
is to install a Linux on it.

I installed a fresh Debian 12, the built-in NIC (BCM5720) is working, it
also can see the BCM57412 card ports, but I have no link for some
reason.

Here are the relevant outputs:

https://pastebin.com/ghbSySfC

As you can see, there is no link detected unfortunately, one of them has unknown speed, the other can see that the speed is 10000Mb/s.

Additional information can be that the server is connected to a fibre
switch, wich is used by several other Windows boxes.

They used the very same fibre cable (LC/UPC - LC/UPC - MM - DX whatever
it means).

What do I miss here?

ens2f0np0 doesn't have a fiber optic cable plugged in.
ens2f0np0 won't work until someone plugs a new cable into it.

ens2f1np1 has a cable plugged in, but no link detected.
ens2f1np1 won't work until the switch on the other side turns it
up.

fiber cables are very easy to damage and fairly easy to
accidentally not plug in completely.

-dsr-

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