hardMultiple ChoiceObjective-mapped
200-201 Practice Question: During a security incident, a network engineer…
During a security incident, a network engineer captures traffic with tcpdump and saves it to a pcap file. The analyst needs to extract all HTTP POST requests containing a specific string in the URI. Which command should be used?
⚠ Common exam trap
Cisco often tests the distinction between reading a pcap file with `-r` versus capturing live traffic, and the trap here is that candidates may forget to include the `-A` flag for ASCII output or the `tcp port 80` filter, leading to incomplete or irrelevant results.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
tcpdump -r traffic.pcap 'tcp port 80' -A | grep 'POST' | grep 'string'
It uses tcpdump with the `-r` flag to read the pcap file, filters for TCP port 80 (HTTP), uses `-A` to print packet payloads in ASCII, and then pipes the output through two grep commands: first to isolate lines containing 'POST' (indicating HTTP POST requests) and second to filter for the specific string in the URI. This combination efficiently extracts only the relevant HTTP POST requests with the target string from the captured traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
tcpdump -r traffic.pcap -X | grep 'string'
Why it's wrong here
-X prints hex and ASCII; not focused on POST URI.
- ✓
tcpdump -r traffic.pcap 'tcp port 80' -A | grep 'POST' | grep 'string'
Why this is correct
Reads pcap, filters HTTP, prints ASCII, then greps for POST and string.
- ✗
ngrep -q -W byline 'POST.*string' port 80
Why it's wrong here
ngrep is not tcpdump, and -W byline might not extract full request.
- ✗
tcpdump -r traffic.pcap -nn 'host 10.0.0.1'
Why it's wrong here
Filters by IP, not HTTP content.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-201 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-201 exam.