@TSK-IT 

I don't think it will work. The router does not support RSTP on LAN ports.

There will be a loop, and the switch can only use Loop Detection to block the data traffic to one of the router's port. But that's not a stable connection and we can't rely on Loop Detection/Protection. 

I'm thinking the only possible solution is to add another switch to your picture, between the router and the two SW1&SW2, so it can do Spanning Tree with the other switches but only have one Ethernet connection to the router.

Hello @Somnus,

thanks for your answer. Unlikely this misses the goal to build a redundancy scenario. Your solution is actual the status quo. But for now everytime i reboot this one root switch, the entire connection to the internet is offline for about 2 or 3 minutes and within i am not able to do maintainance without interruption. But this is the goal, because the grown demand for availability.

In meantime i've tried my outlined solution in a smaller lab situation and it seems to work. A warning about blocked ports did not apear. That suprised me a little, because i expected it like you described. But i dont know, if it works reliabable in productive environment, which my community thread was intended to.

Do you know another solution?

Best regards

  @TSK-IT Hi there!

Did you ever figure out a solution to this?  I'm running a similar config, but I have two core switches set with a RTSP priority of 8192 and the 2nd core set to 12288, but the router still takes control over the uplink, instead of the LAG to SW1.

Have you found a way to explicity have the routers link be the STP Blocked under normal circumstances?

Thanks so much!

  @TSK-IT 

I have been trying to figure out this same problem and it does work if you set the links to the router to be active in RSTP. They detect the path via the router and block it. However in my own experience if the root switch is lost then reconnected Omada doesn't handle this very well and crashes my network when the root comes back online.