port flapping on hEX running RouterOS 6.49.6

Hello,

I’m facing a port flapping issue with a hEX device running RouterOS 6.49.6 and hope you can help me fix the problem.

The context is the following:


  • One of my computer (running Windows 10, genuine license, system up to date) is connected through ethernet (Intel I211 controller) to port ether4 of the hEX device.
  • Ether4 is an access port for vlan420 (ingress filtering on, admit only untagged), and ether1 is used as the trunk).
  • Ether4 is set to autonegotiation (1Gbps full duplex is negotiated).
  • Other devices connected to the hEX are on other vlans
  • Other devices are a printer (ether5, 100Mpbs) and linux machines (Ether2 and ether3, 1Gbps) there is no port flapping problems with these devices

Sometimes right after having booted, sometimes after 5 minutes, sometimes after 20 minutes, the port to which the Windows machine is connected (ether4) starts flapping (link down,then link up after 2 seconds, then again link down after 3 to 5 seconds, rinse and repeat until Windows machine is rebooted.) I cannot find a cause for it.

Here is what I tried so far:


  • Change the cable → issue remains
  • change access port from ether4 to ether2 → issue remains
  • change access port from ether4 to ether3 → issue remains
  • Disconnect the printer → issue remains
  • Disconnect all other devices connected to the hEX → issue remains
  • turn off powersaving for the network adapter in Windows 10 → issue remains
  • limit autonegotiation announcement on hEX side to 1Gbps → issue remains
  • turn off autonegotiation (set manually to 1Gbps on both windows and hEX sides) → no network detected at all…
  • placed a netgear unmanaged Gigabit switch between hEX’s ether4 port and the Windows computer → problem solved, no flapping anymore !

So apparently something’s wrong / uncompatible between the hEX and the computer running Windows… I could leave it “as is” with the switch inbetween, but from a power saving perspective, it’s kind of stupid to have an additionnal device just to connect a single computer…

Has anybody faced the same type of problem ? Do you have any suggestion ?

Thanks in advance,

Update: after having added an unmanaged switch between the hEX and the PC four days ago, there is no more flapping anymore…

Is anybody else facing this type of issue? What could be the causes ? Where should I look to fix it ?