Top 6 Networking Interview Questions
Browse 6 real-world technical and behavioral interview questions about Networking. Review scenarios, edge cases, and architectural best practices.
Your application cannot reach a service that should be up. Walk me through diagnosing it from the shell.
Work up the layers and let each command eliminate a class of cause: resolve the name, check the route, see whether anything is listening, then decide from the failure mode whether packets are being refused, silently dropped, or answered by something that never replies.
Would you use iptables or eBPF for network policy enforcement in a massive multi-tenant Kubernetes cluster, and what are the operational trade-offs?
eBPF-based Kubernetes network policy can enforce hard multi-tenancy with faster identity-aware checks than long iptables chains, but it demands verifier-safe rollouts, fail-closed controls, and strong policy observability.
When would you choose UDP over TCP, given that TCP is reliable and UDP is not?
TCP guarantees an ordered byte stream and pays for it with head-of-line blocking and retransmissions that arrive too late to be useful. UDP is right when a late packet is worthless, when you need multicast, or when you intend to build your own reliability with different trade-offs.
What cost does kernel-bypass networking actually remove, and what do you give up to get it?
Kernel bypass moves packet handling into user space so a market-data read no longer pays a syscall boundary, a kernel-to-user copy, interrupt and softirq handling, or a scheduler wakeup. You pay for it with a core burned on busy-polling, the loss of standard network tooling, and a driver-specific build. It also connects networking to the point an interviewer is testing.
The tooling you would use to fix a network outage runs over the network that is down. How do you break that circularity before it costs you a day?
Separate the layers that can fail together: routing reachability, name resolution, identity and physical access. Then build an access path that shares none of them, keep controls failing static rather than closed, and rehearse the emergency path often enough that it is known to work.
Why does the standard Linux network stack fail at MMO scale, and how do you bypass it using DPDK?
Evaluate the integration of kernel-bypass techniques to handle millions of simultaneous connections and minimise CPU overhead in MMO architectures.