Networking Interview Questions and Answers
Real scenario-based questions, a free networking guide, and practice exercises — free to get started.
Free networking interview questions
A free sample — one beginner, one intermediate, one advanced — with the full answer shown below each question.
BeginnerWhat's the difference between a forward proxy and a reverse proxy?
A forward proxy sits in front of clients, making requests on their behalf to the internet (hiding the client from the server) — common for corporate outbound filtering. A reverse proxy sits in front of servers, receiving client requests and routing them to backend services (hiding the servers from the client) — like Nginx or an ALB in front of an application.
AdvancedYour application intermittently gets connection resets under high traffic, but works fine at low traffic. What would you check?
Check for port exhaustion — under heavy outbound connections (e.g., to a database or external API), the OS's ephemeral port range can run out, especially with short-lived TCP connections not using keep-alive. Check the server's file descriptor limits and TCP connection backlog (somaxconn) too — both are common bottlenecks that only appear under real load.
IntermediateWhat's practically different about TLS 1.3 versus TLS 1.2 for a DevOps engineer configuring a server?
TLS 1.3 removes several outdated, insecure cipher suites (simplifying secure configuration), requires forward secrecy by default, and completes its handshake in one round trip instead of two — meaning less latency on new connections. Practically, it means fewer cipher-suite decisions to get wrong and a small but real performance win.
Learn networking in depth, free to start
A guide covering OSI, DNS, HTTP, ports, SSH, and firewalls — the plumbing behind almost every production outage you'll ever debug. The first page is free for everyone.
- Core Concepts
- DNS Deep Dive
- Load Balancing & Reverse Proxies
- TLS/SSL & Certificates
- Cloud Networking Patterns
- Troubleshooting Network Issues
Practice networking for real, no infrastructure needed
Lock down a ufw rule that exposed Postgres to the internet, or diagnose a real two-layer Postgres remote-connection failure — all graded on real tool output.
Networking interview FAQ
What are the most commonly asked networking interview questions for DevOps?
Interviewers usually describe a connectivity problem — a service that's reachable on one port but not another, Postgres refusing remote connections, DNS resolving but the port timing out — and ask what you'd check first with the real tools (dig, nc, curl), not ask you to define TCP from memory.
Do I need deep networking theory (the OSI model) or just practical skills?
Practical skills matter more day to day, but knowing roughly which layer a problem lives at helps you debug faster — a DNS failure, a port timeout, and a refused connection are three different layers with three different fixes, and interviewers often probe whether you can tell them apart.
How do I tell a DNS problem from a port or firewall problem?
dig/nslookup tests whether the name resolves at all. nc or curl against the resolved IP and port tests whether the port is actually reachable. A timeout usually means a firewall is silently dropping the connection; a quick refusal usually means nothing is listening on that port.
How do I practice networking without a real network to break?
Work through fix-the-firewall exercises and simulated-terminal incidents first — locking down a ufw rule that exposed Postgres, diagnosing a two-layer Postgres remote-connection failure — all graded on real tool output, no real infrastructure needed.
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