Final answer:
To determine where traffic to a specific IP address is being blocked, a technician should use the 'tracert' command, which reveals the path packets take and identifies where they are being stopped along the route.
Step-by-step explanation:
When a technician wishes to diagnose network connectivity issues with a specific IP address and wants to identify where along the path the traffic is being blocked, the command that should be used is tracert (Trace Route). This tool allows the user to track the path that a packet takes to reach an endpoint by sending out packets with incrementing Time To Live (TTL) values. Each router along the path is supposed to reduce the TTL of a packet by at least 1 before passing it on, and when the TTL reaches 0, it should send an Internet Control Message Protocol (ICMP) message back to the source. This process enables tracert to report the presence of each hop along the route to the destination. If the packets stop at a certain hop, you can identify where the communication is being blocked. This is useful for pinpointing network issues and determining latency and bottlenecks in a network path.