Hello,

I am facing an issue on 3 separate RB951G2HND routers that the Ethernet connection to the router via the 5 ports is constantly switching between cable plugged, link ok, cable unplugged . This keeps on repeating. I can't connect to the routerOS via winbox through Ethernet. If i connect to it via WiFi then i can access the routeros. This leads me to believe the issue is with the switch chip.

Additionally in Winbox when connected via WiFi there is no option to set the master port under the Interface tab of the Ethernet. See attached screenshot.

I have around 60 RB951G2HND routers and have faced this issue on 3 of them. I have tried resetting them and different firmware versions but the problem is still there.
I wanted to know if anyone else has faced similar issues or if anyone from Mikrotik can further support. It would be possible for me to ship the faulty boards for further debugging if needed. I would like to know what the cause of this issue is.

Which version of RouterOS? Since 6.41 there is no master port anymore. You must always use a bridge to group wired ports, then bridge (it also has "port" personality) functions as master port functioned previously.

Which version of Routerboot (check in System->Routerboard). If it'd too old, it might be good to upgrade.

Which version of winbox?

At the end of the day, your faulty RB591Gs might suffered from some corrosion or somesuch which is making problems and you'll have to replace them ...

Winbox Ver 3.18
Firmware 6.42.1
Routerboard updated to 6.42.10 - same behavior.
I don't see any visible signs of corrosion/oxidation on the board.

It could be some "cold soldering" some loose joint on the board. A chip or RJ45 pin.