Exercise 2: Why tracert and traceroute Can Disagree on the Same Path — Possible Solution ==================================================================== THE UNDERLYING PROTOCOL DIFFERENCE ------------------------------ Per this chapter's finding-box, "tracert on Windows sends ICMP echo requests, the same protocol family as ping. Traditional traceroute on Linux/macOS sends UDP packets to a high, normally-unused port by default, relying on a 'port unreachable' ICMP response at the final hop to detect arrival." The two tools are testing the path using genuinely different underlying protocols, not just different-looking output for the same test. WHY THAT CAN PRODUCE DIFFERENT RESULTS ON THE SAME PATH ------------------------------ Per this chapter, "a firewall that blocks UDP but allows ICMP (or the reverse) can make one tool succeed and the other fail on the exact same path, for reasons that have nothing to do with the actual destination being reachable." A firewall rule filtering by protocol (ICMP vs. UDP) affects each tool differently, even though neither tool result says anything false - they're each accurately reporting what happens to their own specific protocol along that path. WHY "NOTHING ABOUT THE DESTINATION CHANGED" DOESN'T MAKE THIS A CONTRADICTION ------------------------------ The destination and the physical/routed path can be completely unchanged while a firewall rule still treats ICMP and UDP traffic differently at some point along that path - the discrepancy comes from the protocol each tool uses, not from anything different about the destination itself. WHY THIS WORKS AS AN ANSWER ------------------------------ It names the specific underlying protocol difference between the two tools per the chapter's own finding-box, and explains the mechanism (protocol-specific firewall filtering) that lets identical paths produce different results, rather than attributing the discrepancy to the tools being unreliable or the path itself changing.