Plant six connectivity faults and prove the sequence stops at the right layer

applied · 90 min · Objective 5.1

Task

Break the connection in six different places, one at a time, and confirm that the outward sequence stops at the layer that was broken -- which is the claim the method rests on and the thing that has to be shown rather than assumed.

Steps

  1. Record the healthy baseline in lab/planted/baseline.txt by running the full sequence and capturing every step's output.
  2. Plant six faults one at a time, reverting each before the next: adapter disabled; no address, by isolating the adapter from DHCP; wrong mask; no gateway; no DNS server; and a firewall rule blocking one destination port.
  3. For each, run the sequence and record in lab/planted/runs.csv with header fault,stopped_at_step,expected_step,matched,seconds.
  4. For any mismatch, record in lab/planted/mismatch.md why the sequence stopped somewhere else and what that reveals about the sequence.
  5. Revert every fault, re-run the sequence clean, and record the clean run in lab/planted/restored.txt plus one confirmation line per fault in lab/planted/reverted.txt.

Verify

grep -c . lab/planted/baseline.txt
awk -F, 'NR>1 && NF>=5 {n++} END {print n" planted fault(s)"}' lab/planted/runs.csv
awk -F, 'NR>1 && tolower($4)=="yes" {n++} END {print n+0" stopped at the expected step"}' lab/planted/runs.csv
awk -F, 'NR>1 {print $2}' lab/planted/runs.csv | sort -u | wc -l
grep -c . lab/planted/reverted.txt
grep -c . lab/planted/restored.txt

A baseline, six faults recorded, at least four stopping at the expected step, at least four distinct stopping points, six revert confirmations and a clean run. If every fault stopped at the same step, the faults were planted at the same layer.

Notes

The wrong-mask fault is the instructive one. Depending on which direction the mask is wrong, the sequence stops at the local host or at the external address, and both are correct behaviour from the same misconfiguration.

This is an independent study companion for CompTIA A+ Core 1 220-1201 and is not produced by or endorsed by CompTIA.