FortiSwitch: Spanning Tree Issue - STP instance with ID 15

[urutai]

hello,

We recently installed some FortiSwitch-124E switch units (all with firmware v7.2.3, build0434,221212) in our network, which already had several switches from other manufacturers.
In the network, we have the MSTP protocol enabled and configured on all switches, everything working as it should be. However, when trying to activate this protocol on Fortinet Switches we noticed that these devices automatically create an STP instance with ID 15

The problem is that on some of the other switches we already had, it is not possible to create this ID 15 instance and on Fortinet switches I cannot remove this STP instance, every time it is removed, it returns when the device restarts. Therefore, the STP configuration of the Fortinet switches always differs from the others, preventing protocol convergence.
Is there any way to prevent this instance from being created automatically? How to do this?

[Anthony_E]

Hello urutai,

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible.

Thanks,

[urutai]

Hello Anthony_E,

thanks for the feedback. We are awaiting a response.

[Anthony_E]

Hello urutai,

We are still looking for someone to help you.

We will come back to you ASAP.

Regards,

[AEK]

Hi @urutai 

I don't have a direct answer on this but it is for FortiLink management VLAN.

If I'm not wrong your FortiSwitch is standalone (not FG managed), right? In that case this VLAN may be not useful for you and there should be a way to disable it or just by deleting FortiLink interface if you really don't need it.

[urutai]

Hi, @AEK 

That's right, our FortiSwitch are in standalone mode. Unfortunately I haven't found a way to disable the creation of this STP instance yet. On switches there is no specific interface for or with the name FortiLink. As shown in the image below, the interfaces have activated the FortiLink Discovery feature.

I tried to disable this FortiLink Discovery with the following commands:

---

---

config switch interface
 edit "portXX"
 set auto-discovery-fortilink disable
end

config switch global
  set auto-discovery-fortilink disable
end

however, this feature does not deactivate on the TRK1 (trunk) interface and is reactivated on all interfaces upon restart.
Is this how to disable FortiLink? what am I doing wrong?