Practical tcpdump and dig commands for troubleshooting TLS and DNS issues

A guide highlights practical command-line examples for tcpdump and dig that go beyond what standard man pages offer. The tcpdump examples cover filtering connection setup and teardown packets, extracting the SNI hostname from TLS ClientHello messages, and saving full packet captures for later analysis in Wireshark. The dig examples show how to display DNSSEC records in readable multiline format, produce YAML output for scripts, trace delegation from root servers, and query authoritative servers directly to bypass cached results. The author notes these commands are most useful for failing TLS handshakes, broken DNSSEC validation, machine-readable CI output, and resolving disagreements about DNS answers. The piece encourages readers to keep the relevant commands for their own stack and to share others they rely on.