Hello experts,
I have an ACI fabric and a bunch of Cisco switches connected to it. MST is configured on all these switches. We have configured a dedicated BD/EPG for the native vlan to make it work.
A month ago, we got a network outage because we connected a PVST switch with a better priority than the current MST Root to the ACI. All MST switches blocked its ports connected to the ACI with the error message "%SPANTREE-2-PVSTSIM_FAIL: Blocking designated port Po1: Inconsistent superior PVST BPDU received on VLAN 13, claiming root 4096:e4c7.2214.fac1"
It happens because of PVST inconsistency check, which is part of the PVST Simulation feature on Cisco switches. In order to fix that problem, we disconnected PVST switch from ACI fabric. It happened more than a month ago, but even now the port on Cisco switches connected to the fabric are still working in PVST boundary mode. In PVST boundary mode the Cisco switch generates BPDU in every allowed VLAN on PVST boundary port, so it behaves like a general PVST switch.
Now we have got another problem related to PVST simulation feature. Every time when we reload any Cisco switch connected to ACI we get a 20 seconds network outage. All Cisco switches blocked its ports connected to the ACI with the error message "%SPANTREE-2-PVSTSIM_FAIL: Blocking root port Po1: Inconsistent inferior PVST
BPDU received on VLAN 20, claiming root 32768:5006.0431.1800"
Again, it expected behavior and ports blocked due to PVST inconsistency check, which is described here https://www.cisco.com/c/en/us/support/docs/lan-switching/multiple-instance-stp-mistp-8021s/116464-configure-pvst-00.html
These problems are observed only on Cisco switches (PVST simulation feature is Cisco proprietary) with MST.
In order to fix this issue, I have configured BPDU filter towards all Cisco switches on ACI, but I don't like this workaround at all.
I would appreciate any advice about network design in my case.
