46+ Production Networking & Cloud DNS Interview Questions & Scenarios (2026 Edition)

Q: A web application in a private subnet needs to download updates from the internet, but it keeps timing out. Why?

\"Networking issues can paralyze distributed applications. In our hybrid cloud architecture, we traced this packet path. The interviewer is testing: Public/Private subnet definitions, NAT Gateways, routing.. I structure my answer around systematic triage first, root cause analysis second, and permanent remediation third.\" Key Takeaway: Pro-Tip: By definition, a private subnet does not have a route to the Internet Gateway (IGW) and the instances within it do not have public.

Q: Two EC2 instances in the exact same VPC and subnet cannot ping each other, but they can both reach the internet. What is the most likely cause?

\"When an interviewer asks how I diagnose network connectivity, I follow an outside-in OSI model approach. The interviewer is testing: Security Groups vs Network ACLs, default behaviors.. I structure my answer around systematic triage first, root cause analysis second, and permanent remediation third.\" Key Takeaway: Pro-Tip: Local OS firewall (iptables or firewalld) blocking ICMP..

Q: You type `facebook.com` in your browser. Explain the DNS resolution process step-by-step.

\"In our multi-VPC setup, services in private subnets ran into this exact routing obstacle. The interviewer is testing: Foundational DNS knowledge, caching, root/TLD servers.. I structure my answer around systematic triage first, root cause analysis second, and permanent remediation third.\" Key Takeaway: Pro-Tip: Browser Cache: The browser checks its own DNS cache..

Q: Your company has two VPCs in different AWS regions. You set up VPC Peering between them. From VPC A (10.0.0.0/16), you can reach a server in VPC B (10.1.0.0/16). However, the server in VPC A cannot access the internet *through* VPC B's NAT Gateway. Why?

\"Isolating network failures requires proving whether packets are dropped by route tables, security groups, or stateless NACLs. The interviewer is testing: VPC Peering limitations, transitive routing.. I structure my answer around systematic triage first, root cause analysis second, and permanent remediation third.\" Key Takeaway: Pro-Tip: Provide VPC A with its own NAT Gateway and Internet Route..

Q: What is the difference between an Application Load Balancer (ALB) and a Network Load Balancer (NLB)? When do you use which?

\"Networking issues can paralyze distributed applications. In our hybrid cloud architecture, we traced this packet path. The interviewer is testing: OSI model, Layer 7 vs Layer 4, TLS termination.. I structure my answer around systematic triage first, root cause analysis second, and permanent remediation third.\" Key Takeaway: Pro-Tip: ALB (Layer 7): Operates at the Application layer. It understands HTTP/HTTPS headers, URLs, and cookies. You use it when you need p.

Junior / Associate DevOps [L1] Networking

⚡ Scenario networking-q001-a-web-application-in-a-private-subn

Networking Q1: A web application in a private subnet needs to download updates from the internet but it keeps timing out Why [L1]

By definition, a private subnet does not have a route to the Internet Gateway (IGW) and the instances within it do not have public IPs....

#Networking #Networking #L1

All Networking & Cloud DNS Scenario Questions (46)