RSTP not working properly on Port 14

[ftips]

Hello
We are using port 14 with SFP module as our uplink to Mikrotik Router. Problem is with RSTP, it is selecting a port with a longer route as its' ROOT port. In fact, it is selecting a port that has to go through two backhauls and another Netonix switch before that path gets back to Mikrotik router. No matter what I try, Port 14 will never show as root or even as a designated port. I've tried port priority, path cost. I have also tried disabling RSTP on all interfaces except port 14 and still will not elect as root or designated. Running software version 1.5.5

[mike99]

cost of each port ? For main and alternate path ?

[ftips]

All is set to priority 128 and auto on cost. Tried changing priorities and cost but port 14 never shows up as designated, root or alternate

[ftips]

Screenshot of STP Tab

Here is a screenshot

[mike99]

Is cc:2d:e0:cc:62:77 the Mikrotik you would like as gateway ? The one connected to port 14 ? I presume not.

STP don't behavior like an IGP, by exemple OSPF. In STP, lowest global priority win as root device and every device participating in STP will take the shortest path to reach the root device. Since this Mikrotik (cc:2d:e0:cc:62:77) have a global cost of 20480, it win as root and the whole STP L2 network will behavior to reach this device with the lesser cost.

To solve this, you can isolate the L2 network to make sure cc:2d:e0:cc:62:77 don't affect this switch behavior.

P.S. : Forget about priority, the cost is what larger network need to use. Priority is only usefull in case of equal cost path and won't affect the STP behavior of other switchs.

[ftips]

I do want the traffic from this switch to use Mikrotik 62:77 as its root bridge. Port 14 is directly connected to it. the other paths are much longer since they go through two wireless backhauls to get back to 62:77

[mike99]

What is the cost of every device on the chosen STP path ? If set to default, not all device use the same default cost value,
To be able to help, we would need the stp config and show stp output of every devices that participate to the stp network with a schema to be able to figure out why. Please also indicate which port is in blocking mode.