200-201 Security Monitoring Practice Question
An analyst uses 'tshark -r capture.pcap -Y "http.request.method == POST"' to display only HTTP POST requests. This is an example of a:
⚠ Common exam trap
Cisco often tests the distinction between display filters (`-Y`) and capture filters (`-f`), trapping candidates who confuse the `-Y` flag with a capture filter because both can filter packets, but only capture filters discard data at the point of acquisition.
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
✓
Display filter
The `-Y` flag in tshark applies a display filter, which operates on packets already read from the capture file. Display filters use a syntax based on protocol fields (e.g., `http.request.method == POST`) to show or hide packets in the output without altering the underlying capture data. This is distinct from capture filters, which discard packets at the kernel level before they are stored.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Statistical filter
Why it's wrong here
Statistical filters produce protocol hierarchy or conversation summaries via -z, not packet selection. The -Y expression selects individual HTTP POST packets for display, which is a display filter. Statistical filtering would be correct when the analyst needs traffic counts or endpoint statistics rather than matching specific packets.
- ✗
Read filter
Why it's wrong here
A display filter is applied after capture to select which packets tshark prints; a read filter is a capture-time construct in tools such as Wireshark's dumpcap, restricting what is written to disk. Read filters are correct when storage or capture overhead must be limited during collection.
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Capture filter
Why it's wrong here
Capture filters use BPF syntax and are set with -f before capture begins, discarding non-matching packets at the interface. The -Y flag filters already-captured frames for display, so nothing is dropped. A capture filter would be correct when the analyst must limit what is written to the pcap file.
- ✓
Display filter
Why this is correct
The -Y flag applies a Wireshark display filter, which restricts which decoded packets tshark prints without altering what was captured. Capture filters, by contrast, use BPF syntax and discard traffic at collection time, so they cannot be applied to an already-saved pcap.
Visual reference
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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.