Hi
I have checked the Switch config which is connected to Core switch 2:3
I found stp is configured on uplink ports (53,54) as below:
configure stpd STPD-X add vlan X ports 53 pvst-plus
configure stpd STPD-Y add vlan Y ports 53 pvst-plus
configure stpd STPD-Z add vlan Z ports 53 pvst-plus
configure stpd STPD-X add vlan X ports 54 pvst-plus
configure stpd STPD-Y add vlan Y ports 54 pvst-plus
configure stpd STPD-Z add vlan Z ports 54 pvst-plus
configure stpd STPD-X tag 4000
enable stpd STPD-X
configure stpd STPD-Y tag 200
enable stpd STPD-Y
configure stpd STPD-Z tag 900
enable stpd STPD-Z
whereas on core switch port 2:3 stp is not configured.