I went through an infrastructure-focused interview where the discussion started with Linux fundamentals like file permissions/ownership (chmod, chown, umask), basic bash scripting, and daily admin commands (ps/top, grep/awk/sed, tar, systemctl, journalctl). Then it moved into networking concepts like protocols + OSI mapping, and they went deep into TCP headers/flags, 3-way handshake (SYN → SYN/ACK → ACK), and how troubleshooting changes when ICMP works but TCP fails (or vice versa). After that, they asked practical questions on load balancing + reverse proxy, mostly around Nginx—how to configure server blocks, upstream, proxy_pass, and how to fix common issues like 403/404 by checking root path, index file, permissions, and Nginx config under /etc/nginx (nginx.conf / sites-enabled). The final part was pure troubleshooting using nmap, tcpdump, and Wireshark, including scenarios like “IP known but ping not working” and “ping works but website not opening”, so I explained the step-by-step flow: routing/DNS, firewall rules, port checks (80/443), service validation (curl), and packet analysis. Overall it felt hands-on and real-world oriented, focused on fundamentals + how you isolate the root cause.