In OPC Classic, what is a significant drawback related to firewalls?

In the context of OPC Classic, the significant drawback related to firewalls is associated with dynamically assigning TCP ports. OPC Classic, which primarily uses DCOM (Distributed Component Object Model) for communication, relies on a dynamic port allocation method that can make firewall configuration challenging.

With dynamic port assignments, when a client attempts to communicate with a server, the server can open any port for the session instead of using a single, fixed port. This unpredictability can create complications for firewall administrators who must allow traffic between specific devices. Since the ports can change, it is difficult to configure firewalls to permit the necessary traffic, increasing the risk of connectivity issues or security concerns, as firewalls typically operate more effectively when dealing with fixed port assignments.

In contrast, static port assignments allow for easier firewall rules since the ports do not change, making management more straightforward. Special configurations might be needed for DCOM and its components, but the root problem with firewalls primarily lies in the aspect of dynamic TCP port assignment. Thus, the dynamic nature of TCP port assignments in OPC Classic creates a significant vulnerability when it comes to securing and managing firewalls.