During the first call, I was prompted at first with very basic questions about operating system and networking, then in went deeper on questions like: "what happen if you type telnet www.google.com", the questions within this one ranged from "tell me the process uses the OS to create that connection" to "how the data travels through the internet to reach the target server".
The second call went even deeper in troubleshooting Linux, web servers, dns, load balancing, IP, routing and so on. Also, the recruiter asked me to code some python and bash scripts in order to solve some problems made for that interview