Configuration of Network

[awasis]

I have implemented a network which consists of two core switches stacked  and some 20 access switches aruba 2930m. All the access switches are connected to the core switch through two interfaces each one to core 1 and other to core 2.  using LACP.

I have set the core switch as the root bridge with priority 0 for STP,  and i have configured all access switches with Rapid PVST. But what i have noticed that my root is changing frequiently 

: VLAN 16 - Root changed from 32768: 64e881-c70cc0

: VLAN 1 - Root changed from 32768

I am getting these msgs in every switch , I need expert opinion how to fix this and what STP should be configured to make it stable network. 

[support_s]

Hello,

Thank you for Posting! HPE Networking forum has moved to Aruba Airheads Community and for HPE networking and Aruba product queries, request you to visit and post your query here.

You can refer to this link for more details.

Please click on "Thumbs Up/Kudo" icon to give a "Kudo".

Thank you for being a HPE valuable community member.