hi Benha,
To prevent unauthorised usage of the switch/STP, you can configure either an “Allow” list or a “Disallow” list, with the OPC as the criteria. In the “Allow” list, you need to include Point Codes of ALL nodes that are to use the STP. You need to be very careful with this. Missing out on any point codes will result in service outage. You use a “Disallow” or “Block” list when you want to prevent usage by specific signaling points.
In addition, you can create a chain of criteria, eg “Allow” this OPC, but “Allow” only this list of DPCs for this OPC. The switch supplier should be able to furnish you with more details.