Hello,

we are at the end of our wits so we may as well ask.

We we using two Windows Server 2016 machines, fully updated and connected to a Mikrotik CRS328-24P-4S device with copper 10G connections, fully updated to stable version. The SFPs are S+RJ10 model. The problem happens seemingly randomly, but it manifests so that the server goes to Cable Unplugged state on one of the interfaces.

We have so far reinstalled the server several times, upgraded all of the firmware. At the moment, we have a completely fresh installation of WS2016 and it is also in Cable Unplugged state on ONE of the interfaces. Not both, just one. The NIC on the server has two interfaces and one of them is working nicely. The other server (identical hardware) also has two interfaces and they are also working nicely.

We've tried to rotate the SFPs, but when an interface goes to Disconnected state, placing another SFP which worked nicely in, say SFP2, does not work in SFP1. However, occasionaly after replugging the interface does come alive.

We tried resetting the switch and it did not help. We also tried clearing the ARP, but no luck.

It mostly happens on SFP1, but we have replaced the switch with a brand new one and that did not prevent it and, like I said, we tried rotating the SFPs and that does not solve the problem.

Thanks for any suggestions!

EDIT: I forgot to mention. When we set Mikrotik to Autonegotiate 1G and the NIC on the server to Static 1G, it connects normally. All other combinations of 1G and 10G connections yield either in Unknown Network or Cable Disconnected.