Network Engineer Interviews: How to Explain Subnetting, Routing and Troubleshooting Out Loud

Network engineer and network support interviews have a pattern that catches many candidates off guard. You may know what a subnet mask does, what a default gateway is and how traceroute works, but the interviewer rarely stops at the definition. They ask you to explain it, apply it to a scenario, and then troubleshoot something that went wrong. This guide covers how to prepare for that. 1. Expect "explain it like I'm a colleague" questions Typical openers are simple: What is the difference between a switch and a hub? What does ARP do? Why would you use a private IP range? The trap is answering with a memorised sentence. A stronger answer adds one practical example. For ARP, say what happens when a host knows the IP of its gateway but not the MAC address, and what you would see in a packet capture. That one sentence of context shows you have actually used it. 2. Practise subnetting until it is boring Many interviews include a quick subnetting question: how many usable hosts in a /27, which subnet does 10.1.5.130/26 belong to, or how would you split a /24 for four departments. Do these on paper every day for a week. Say your steps out loud as you go, because the interviewer cares as much about your method as the number. 3. Have a troubleshooting framework Scenario questions such as "a user can reach internal sites but not the internet" are where interviews are won or lost. Walk through the layers: physical link, IP configuration, gateway reachability, DNS resolution, then firewall or proxy rules. Name the command you would run at each step (ipconfig or ip a, ping the gateway, nslookup, tracert). Interviewers want a calm, ordered process, not a lucky guess. 4. Know your routing and switching basics Be ready to compare static and dynamic routing, explain when OSPF is preferred over RIP, describe VLANs and trunking, and outline what STP prevents. If you have a CCNA or similar, link each answer to a lab you built. "I set up inter-VLAN routing in Packet Tracer and broke it on purpose to see what happened" is a memorable line. 5. Prepare two real incident stories Behavioural questions still appear in technical interviews. Prepare a story about an outage you helped fix and one about a change that went wrong. Use the STAR format, keep the technical detail accurate, and end with what you changed afterwards. 6. Practise the live format Phone and video interviews make it harder to draw diagrams, so practise describing a topology in words. Tools can help here too: Linkjob AI (https://linkjob.ai) gives real-time help during live job interviews and technical interviews, which some candidates use to stay structured when a scenario question turns complicated. Final tip At the end, ask about the network itself: what equipment they run, how changes are approved, and how on-call works. It shows genuine interest and gives you a realistic view of the job.