Network engineer interviews go deeper on networking than a general software role — routing and switching, subnetting, protocols, VLANs, and methodical troubleshooting. Here are the network engineer interview questions that actually get asked. (See also our computer networks guide.)
Fundamentals
- The OSI model and TCP/IP — layers and what each does.
- TCP vs UDP; the three-way handshake.
- How does DNS, DHCP, and ARP work?
- What happens when you type a URL (the full path)?
Routing & switching
- Router vs switch vs hub.
- Routing protocols — OSPF, BGP, static vs dynamic.
- VLANs and trunking; STP (Spanning Tree).
- NAT and PAT.
Subnetting & troubleshooting
- Subnetting and CIDR — be ready to calculate.
- Public vs private IP; IPv4 vs IPv6.
- Troubleshooting tools — ping, traceroute, nslookup, netstat.
- "A user can't reach a server — how do you diagnose it?"
How to prepare
Network rounds are verbal and troubleshooting-heavy. Practise explaining protocols and diagnosing connectivity issues out loud. Greenroom runs spoken technical interviews that follow up on your reasoning. Pair it with our networks guide.
Frequently asked questions
What questions are asked in a network engineer interview?
Network engineer interviews cover the OSI and TCP/IP models, TCP vs UDP and the three-way handshake, DNS/DHCP/ARP, routing vs switching, routing protocols (OSPF, BGP, static vs dynamic), VLANs, trunking and Spanning Tree, NAT and PAT, subnetting and CIDR calculations, IPv4 vs IPv6, troubleshooting tools (ping, traceroute, nslookup), and connectivity diagnosis scenarios.
What is subnetting and why is it important?
Subnetting divides a larger IP network into smaller subnetworks by borrowing host bits for the network portion, defined with CIDR notation like /24. It improves address efficiency, reduces broadcast domains, and enables better security and routing. Network engineer interviews often include subnetting math — calculating subnet masks, usable host counts and network ranges — so be ready to do it quickly.
What is the difference between a router and a switch?
A switch operates mainly at Layer 2 (data link), forwarding frames within a local network based on MAC addresses, connecting devices in the same network segment. A router operates at Layer 3 (network), forwarding packets between different networks based on IP addresses and making routing decisions. In short, switches connect devices within a network; routers connect and route between networks.
How should I prepare for a network engineer interview?
Master the OSI/TCP-IP models, routing and switching, subnetting math, and protocols like DNS, OSPF and BGP, and practise methodical troubleshooting (where in the path is the failure). Rehearse explaining protocols and diagnosing connectivity issues layer by layer out loud with a voice-based mock interview that follows up, since these rounds are verbal and troubleshooting-heavy.