switch running RSTP spanning-tree type cut itself from the rest of network

[Andrey128]

Switch runs RSTP (via MST setting) and it shows that one of its uplinks is in "BLK" status, as expected and another uplink is in "BKN", which is not expected and cuts this switch from the network. This switch runs with Aruba switches, which run RSTP spanning-tree.

How in this case unlock uplinks of Cisco switch which runs RSTP (via MST setting) 

[marce1000]

        - Check the logs when this happens, look for additional info's if any.

 M.

[paul driver]

Hello
you have a classic stp pvst simulation issue

the mst-pvst boundary port cannot be a root port and a cist root switch at the same time and that’s exactly what’s happening 

Either make the mst have a lower priority value for it IST and MST instances then the pvst root switch vlan 1 or have the pvst root switch stp priority values more preferred then the mst root switch for vlan 1 but lesser value for all its own other vlans 

[Andrey128]

thanks for details,

I've tried to set low priority (4096x15=61440) on this switch. Settings on this switch are pretty straightforward:

spanning-tree mst configuration
name "switch's hostname"

spanning-tree mst 0 priority 61440

On site Aruba is core switch and root of RSTP spanning tree. I found out that there are also 4 access switches, which are running PVST, just running per command:

spanning-tree mode rapid-pvst

Looks to me these all switches, including impacted switch, are interact with each other via CISCO’s feature called “PVST simulation”.

[paul driver]

Hello
The CIST root for the stp domain doesn’t have to be the boundary switches between arubas and cisco any switch can become this but it sounds like you now have multiple stp regions with the aruba also having switches running rstp and mstp modes, suggest you make all aruba either rstp or mst and not both
Keep in mind when your using MST you really don’t need to prune any vlans from the trunks, this can cause blackholing of traffic, as now stp is ran per mst instance not per vlan

Have a look at this