Which troubleshooting method is not based on the TCP/IP reference model?

The troubleshooting method identified as not based on the TCP/IP reference model is configuration comparison. This method entails examining and contrasting network configurations to identify discrepancies or issues. It focuses on the setup and parameters of network devices rather than using layers defined by the TCP/IP model, which is specifically structured to address and facilitate communication within various layers of networking.

The other methods—top-down, bottom-up, and replacement—are inherently tied to the TCP/IP model. The top-down approach begins troubleshooting from the application layer and works downward to lower layers, while the bottom-up method starts from the physical layer and ascends the hierarchy. Both of these methods utilize the layers of the TCP/IP model, leveraging its structure to isolate and fix problems in network communication.

Replacement, while less conventional compared to the first two, also implies utilizing the model in terms of systematically substituting components or layers to diagnose faults, demonstrating a reliance on layer-specific functionality.

Thus, configuration comparison stands out as the only method here that does not inherently utilize the specific layered approach which characterizes the TCP/IP reference model.