Exercise 2: Confirming Ticket 2 Was a Firewall Issue, Not the App — Possible Solution
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WHAT RULED OUT THE APPLICATION ITSELF
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Per this chapter, DNS resolved correctly and a ping succeeded from the
new Wi-Fi network - both lower rungs were confirmed healthy. Then a
direct port check to the exact same destination and port succeeded
from the wired network but hung with no response from the new Wi-Fi
network. Since the app was demonstrably reachable and working (from
wired), the app itself could not be the problem - only something
specific to the Wi-Fi network's own path to it could explain the
difference.

WHY TESTING FROM BOTH NETWORKS WAS THE KEY STEP
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Per Chapter 7's own reasoning, reused directly in this ticket, "a port
that opens cleanly from inside the same network as the server, but
times out from outside it, is strong evidence for a boundary firewall
or a cloud security group specifically - not the service itself, which
is demonstrably working for at least one source." Testing only the
Wi-Fi network alone would have shown a failure with no way to tell
whether the app, the network, or a boundary rule was responsible;
testing both and comparing produced a result the app-only test
couldn't have given.

WHAT THE CONFIRMED CAUSE TURNED OUT TO BE
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Per this chapter, handing off the specific subnet/destination/port
evidence to the network team confirmed the reporting app's
security-group rule was scoped to the old wired subnet and had never
been updated to include the new Wi-Fi range - a source-scoped firewall
rule, exactly the pattern Chapter 7 described, caused by an oversight
during rollout rather than the application being broken.

WHY THIS WORKS AS AN ANSWER
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It identifies the specific evidence (the app working from wired,
failing only from Wi-Fi at the port-check level) that rules out the
application, and explains why comparing vantage points specifically -
not just testing from one location - was what actually produced that
evidence.