XK0-006 Troubleshooting Practice Question
An administrator needs to capture network traffic on interface eth0, filter for packets to/from host 10.0.0.1, and save the output to a file for later analysis. Which command should be used?
⚠ Common exam trap
Test-takers frequently confuse `src` and `dst` filters as sufficient for capturing all traffic to/from a host, forgetting that `host` is the correct primitive for bidirectional capture.
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 -i eth0 host 10.0.0.1 -w capture.pcap
The `tcpdump` command with the `host` filter captures all traffic (both source and destination) to or from the specified IP address, which matches the requirement to filter for packets to/from host 10.0.0.1. The `-i eth0` specifies the interface, and `-w capture.pcap` writes the output to a file for later analysis.
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 -i eth0 src 10.0.0.1 -w capture.pcap
Why it's wrong here
The src filter captures only packets originating from 10.0.0.1, omitting replies and traffic sent to it, so the capture is incomplete. Specifying a single direction is correct when you deliberately want one-way traffic, such as observing outbound requests from a specific client only.
- ✗
tcpdump -i eth0 dst 10.0.0.1 -w capture.pcap
Why it's wrong here
The dst filter captures only packets addressed to 10.0.0.1, discarding traffic originating from it, so the capture misses half the conversation. A one-directional filter is right when you specifically need inbound packets to a host, for example diagnosing whether requests reach a server.
- ✓
tcpdump -i eth0 host 10.0.0.1 -w capture.pcap
Why this is correct
tcpdump -i eth0 host 10.0.0.1 -w capture.pcap binds capture to eth0, applies a host filter matching traffic in either direction to or from 10.0.0.1, and writes raw packets to capture.pcap for later analysis, satisfying all three requirements.
- ✗
tcpdump -i eth0 -n host 10.0.0.1 -w capture.pcap
Why it's wrong here
-n disables name resolution but still works; however the question does not require -n.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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