Hey all, good news. We found what, we think, is the culprit.Basically, we were running ubuntu 20.04 with the 5.4.0-136-generic Kernel. Upon upgrading to the HWE stack, we switched to kernel 5.15.0-60-generic, and since that the interfaces work as intended.   I'm leaving logs & versions if anyone has the same issue.   Here's the DMESG output before the update when shutting off one of the links to the server :   Here's DMESG output after the kernel update, we can clearly see that only the shut-off interface cuts off :   References : [URL]#Server-1   Thanks, Charles, for your prompt answer. Take care. 
Hello all, I've got a strange behaviour on two of my XR11. They have a BCM57504 4*SFP+/SFP28 mezzanine card. I've got 4 SFP+ 10G-LR duplex fibre plugged in on the two servers, going to a Cisco Nexus 3064 Switch. When you plug or unplug the fibre on one of the SFP, all the other interfaces on the Broadcomm card flap off and on. This causes, as far as I know, a loss of service for the traffic going through those interfaces (switch sees the flap, and so does DMESG).   (Weirdly, the eno8303np0 doesn't flap now, but it did earlier, the only difference I can see is that this interface has a static IP, while the others are used for L2 traffic and bridged to virtual interfaces).   The servers are running Ubuntu Server 20.04.5 and one of them has the latest 22.31.13.70 firmware provided by Dell installed, while the other has a slightly lower version.  I've tried autoneg off, flow control off,  another switch instead of the N3064.  At this point, I'm still investigating, but if anyone has feedback on this issue, I'd be glad to hear it.   Best Regards,   Tanguy
Dell XR11 Broadcomm BCM57504 NIC Flap on all interfaces when connecting fibre