Network Troubleshooting and Tools

Hands on skills for diagnosing and resolving network problems using standard command line and packet analysis tools. Topics include systematic troubleshooting workflows (start with reachability tests and escalate to captures), use of ping and traceroute to verify connectivity and routing paths, netstat and ss to inspect sockets and listening ports, arp and interface commands to check layer two mappings and interface state, router and switch show commands to view routing tables and interface status, and DNS troubleshooting using nslookup and dig. Deep packet capture and analysis with tcpdump and Wireshark is covered, including capture filters, interpreting packet headers and flows, identifying retransmissions, latency sources, and protocol errors. Emphasis is on interpreting tool output, correlating results across layers, and choosing the right tool at each step of an investigation.

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AWS Compute and Networking

Covers design and operational knowledge of Amazon Web Services compute and network components. Candidates should understand Amazon Elastic Compute Cloud instances including instance families, sizing considerations, and pricing models such as on demand, reserved, and spot instances. Knowledge of Amazon Machine Images and launch templates, network interfaces, security groups, route tables, and Virtual Private Cloud architecture including public and private subnets, NAT gateways, and peering is expected. Expect questions on load balancing options including Application Load Balancer and Network Load Balancer, autoscaling groups and policies for availability and cost optimization, and hybrid connectivity patterns such as VPN and Direct Connect. Candidates should also be able to reason about high level multi tier application architectures on AWS, security and networking trade offs, and common infrastructure as code and automation approaches used to provision and manage these resources.

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Infrastructure as Code Tools

Practical skills for authoring, deploying, and managing Infrastructure as Code templates and configurations across cloud platforms. Candidates should be able to author, read, and modify templates or configuration files for native platform tools such as AWS CloudFormation, Azure Resource Manager templates or Bicep, and Google Cloud Deployment Manager, as well as for multi cloud tools such as Terraform. Key areas include file formats such as YAML and JSON, declaring resources, passing parameters or variables, and emitting outputs, together with expressing resource dependencies, conditions, and mappings. Candidates should be able to write templates for common infrastructure patterns including networking such as virtual private clouds, subnets, and security groups, compute resources such as virtual machines and instances, and storage resources such as buckets and storage accounts. They should know how to deploy templates to create stacks or equivalent constructs, perform stack updates and change sets or plan and apply workflows, handle rollbacks and deletions, and manage state for tools that require it including remote state and state locking. Additional important skills are modularization through nested stacks or modules, template validation and linting, integration with continuous integration and continuous delivery pipelines, drift detection and remediation, and basic troubleshooting of template errors and deployment failures. Interview tasks may include writing or modifying short templates, explaining the lifecycle of a deployment, and comparing trade offs between native templates and multi cloud tooling.

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Containerization and Virtualization Trade Offs

Examines trade offs between containers and virtual machines and the complexity of orchestrated environments. Topics include hypervisor and virtual machine basics, container isolation and resource models, performance and overhead comparisons, security and attack surface differences, when to prefer virtual machines versus containers, single container versus orchestrated multi container setups, operational complexity versus benefits, and criteria for selecting the appropriate platform at different scales.

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Internet Protocol Suite Basics

Covers fundamental networking concepts centered on the Internet protocol suite and how its layers map to practical network functions. Topics include comparison of layering models, link layer operation and address resolution, Internet layer addressing and routing including Internet Protocol version four and Internet Protocol version six, subnetting and classless interdomain routing, transport layer semantics such as the Transmission Control Protocol three way handshake, congestion control and reliability, User Datagram Protocol use cases, common control protocols such as the Internet Control Message Protocol and address resolution mechanisms, network address translation, sockets and port concepts, domain name resolution, dynamic host configuration approaches, fragmentation and maximum transmission unit considerations, packet encapsulation and decapsulation, and basic troubleshooting and diagnostic concepts. Interviews assess conceptual understanding and the ability to reason about packet flow, addressing, and protocol behavior under failure or attack conditions.

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Network Protocols and Encapsulation

Comprehensive knowledge of network protocol stacks and layering, including the Open Systems Interconnection model and the Transmission Control Protocol and Internet Protocol suite. Candidates should understand protocol purposes and behaviors at each layer, including connection oriented and connectionless transport, address resolution, discovery and multicast management, and control plane messages. Know common protocols such as the User Datagram Protocol, Internet Control Message Protocol, and Internet Group Management Protocol and how they differ in reliability, ordering, and use cases. Be familiar with tunneling and encapsulation technologies and their tradeoffs, including Virtual Private Network, Generic Routing Encapsulation, Multiprotocol Label Switching, overlay network technologies such as Virtual Extensible Local Area Network, Generic Network Virtualization Encapsulation, and Network Virtualization using Generic Routing Encapsulation. Understand encryption and integrity options at the network layer such as Internet Protocol Security and at the transport layer such as Transport Layer Security and Secure Sockets Layer, including tunnel versus transport modes. Be able to reason about encapsulation overhead, maximum transmission unit and fragmentation, latency and throughput implications, path characteristics, compatibility and interoperability, and typical deployment patterns for site to site tunnels, remote access, data center overlays, and network virtualization.

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Static Routing and IP Configuration

Configure static routes on routers to direct traffic. Understand route syntax, routing table priorities, and how to verify traffic is taking the intended path. Configure IP addresses, subnet masks, and default gateways on devices to ensure Layer 3 connectivity.

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Amazon Web Services Core Services

Comprehensive knowledge of the foundational Amazon Web Services that are commonly used to design, deploy, and operate cloud applications. This includes compute services such as Amazon Elastic Compute Cloud for virtual machines and instance families, Amazon Web Services Lambda for serverless functions, and Amazon Elastic Beanstalk for managed application platforms; storage services such as Amazon Simple Storage Service for object storage, Amazon Elastic Block Store for block volumes, and Amazon Elastic File System for shared file storage; database services such as Amazon Relational Database Service for managed relational databases, Amazon DynamoDB for NoSQL, and Amazon ElastiCache for in memory caching; networking and content delivery including Amazon Virtual Private Cloud networking concepts, subnets, security groups, load balancers, and Amazon CloudFront; container and orchestration options such as Amazon Elastic Container Service and Amazon Elastic Kubernetes Service; and management and security services including Identity and Access Management, Amazon CloudWatch monitoring and logging, Auto Scaling, and cost and service limit considerations. Candidates should understand core service characteristics, common configuration choices and trade offs, operational considerations such as high availability and fault tolerance, basic security and compliance approaches, performance and cost optimization, and guidance for selecting one service over another for typical application patterns.

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Cloud Infrastructure Knowledge (AWS/GCP/Azure)

Have working knowledge of at least one major cloud platform: common services (EC2/Compute Engine, RDS/Cloud SQL, S3/Cloud Storage, Load Balancers, VPCs, networking), typical failure modes, and how to troubleshoot within that platform. Understand concepts like availability zones, regions, and cross-region failover.

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Windows Service and Process Management

Administering and troubleshooting Windows services and processes. Topics include viewing and managing running processes and resource usage with Task Manager and performance monitoring tools, using command line and PowerShell commands to list, start, stop, and restart services, and understanding service configuration such as startup types including automatic, manual, and disabled. Additional areas include service dependencies, recovery and restart options, service permissions and accounts, diagnosing service related errors using the Event Viewer and logs, and strategies for resolving resource contention, hung processes, and service failures.

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GCP Core Services and Architecture Basics

Core Google Cloud Platform services and architecture concepts, including Compute Engine, Kubernetes Engine (GKE), App Engine, Cloud Functions, Cloud Run, Cloud Storage, BigQuery, Pub/Sub, Cloud SQL/Spanner, and IAM. Covers foundational cloud architecture topics such as projects and resource organization, VPC networking (regions, zones, subnets), identity and access management, security considerations, and scalable design patterns for cloud-native applications on GCP.

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Network Design and Security Architecture

Design secure and reliable network and security architectures for cloud environments. Topics include virtual network and subnet design, segmentation and firewall policies, private connectivity patterns, load balancing and failover, encryption in transit and at rest, key management fundamentals and integration with key vaults, identity and access management boundaries, denial of service protections, network monitoring and logging, and compliance and regulatory controls such as data residency and auditability. Interviewers look for practical trade offs between usability security and operational complexity.

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Azure Core Services Overview

Demonstrate familiarity with the primary categories of Azure services and the common offerings within each category. Explain compute options such as virtual machines, App Service, and Azure Functions; storage options such as blob storage, file shares, queue and table storage; networking constructs such as virtual networks and load balancers; and database offerings such as Azure SQL Database, Azure Database for PostgreSQL, and Cosmos DB. Also be familiar with security and identity tools like Azure Key Vault and role based access control, and with monitoring solutions such as Azure Monitor and Application Insights. For each category explain typical use cases, operational trade offs, and basic selection criteria based on control, scalability, cost, and maintenance burden.

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Kubernetes and Container Orchestration Fundamentals

Core knowledge of container orchestration with a focus on Kubernetes fundamentals and everyday operations. Candidates should understand the role of orchestration and why it is used at scale, and be familiar with core Kubernetes objects including pods as the smallest deployable unit, deployments and replica management, replica sets, services for inter pod communication and service discovery, config maps and secrets for configuration and secret management, and the basic lifecycle of containerized applications. Coverage includes deployment and scaling workflows, rolling update and rollout strategies including rollbacks, common deployment patterns such as blue green and canary, and basic health checks and probe concepts. Practical operational skills include common kubectl commands for deploying, inspecting, scaling and debugging applications, reading pod logs and events, describing resources, port forwarding, and diagnosing common failure modes. Candidates should also understand high level trade offs between using managed cloud provider Kubernetes services and operating self managed clusters including operational overhead, upgrades, cost, and reliability considerations. The scope focuses on fundamentals and day to day operations and excludes advanced cluster administration topics such as custom operators, admission controllers, control plane internals, and deep platform level configuration.

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Link Layer Troubleshooting

Troubleshooting at the link layer and local network segment. Topics include Address Resolution Protocol operation and neighbor tables, Media Access Control addressing and switch forwarding behavior, duplicate address detection and gratuitous neighbor announcements, spanning tree protocol related issues, duplex and speed negotiation failures, interface flapping, broadcast storms, and physical media faults. Candidates should know how to inspect neighbor and media access control tables, use link diagnostics such as ethtool, and capture link layer traffic to identify root causes.

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Large-Scale Consumer Device Infrastructure and Operations

Assess a candidate's understanding of the scale, constraints, and distinctive operational challenges of running infrastructure for a company that manufactures and ships large volumes of consumer hardware devices, from managing hundreds of millions to billions of device identities to building a global data center and edge footprint that keeps those devices online and updated. Areas to address include privacy first architecture and telemetry minimization, staged device update and distribution rollouts, secure device attestation and key management, zero trust segmentation and defense in depth, and capacity planning for product launch spikes and other sudden demand surges. Interviewers expect references to concrete infrastructure trade offs and design patterns such as regional edge caching, multi region replication and consistency choices, canary and staged rollout strategies for firmware or software updates, and operational practices for safe change rollout and incident response when a defect or outage can affect millions of devices simultaneously. The assessment evaluates systems thinking across hardware and software boundaries, cross functional collaboration, and the ability to propose scalable, privacy aware, resilient designs that hold up at consumer device scale.

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Network Troubleshooting and Root Cause Analysis

Covers structured, multi layer approaches to diagnosing complex network and cross component failures. Candidates should demonstrate how they characterize incidents, assess scope and impact, reproduce problems when safe, form testable hypotheses, and apply systematic elimination to isolate the root cause. Expect discussion of packet capture analysis, path and flow troubleshooting, interpreting router and switch show commands, checking forwarding information and ARP tables, correlating syslog and application logs, verifying Domain Name System and name resolution, and identifying configuration errors, access control or firewall blocks, routing and forwarding anomalies, MTU and performance issues, and intermittent faults. Candidates should describe tooling and telemetry patterns they use to validate hypotheses, how they collaborate with application and infrastructure teams to eliminate components, how they document findings, and how they drive remediation and post incident reviews to prevent recurrence.

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Cloud Architecture Fundamentals

Fundamental concepts and design patterns for cloud based systems and services. Topics include core service categories such as compute, storage, networking and databases, virtual machines and containers, serverless computing, managed services, and infrastructure as code. Understand deployment and service models including infrastructure as a service, platform as a service, and software as a service. Evaluate architectural patterns including monolithic, microservices, and serverless approaches, and how they influence scalability, availability, reliability, performance, security, and cost. For more senior roles include distributed systems concepts, consistency and partitioning models, trade off analysis, fault isolation, observability and operational practices in cloud native design.

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Understanding the Company's Infrastructure Context

Research the company's public infrastructure information (engineering blog, tech talks, published case studies, job description). Understand what systems they operate at scale, what problems they likely face, and what your role would contribute to.

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Networking Fundamentals and Troubleshooting

Comprehensive coverage of core computer networking principles and the practical diagnostic and operational skills required to design, operate, and troubleshoot production systems. Fundamental concepts include the Open Systems Interconnection model layers, the Transmission Control Protocol and the Internet Protocol stack, the User Datagram Protocol, socket and port semantics, address notation and subnetting, Network Address Translation, Dynamic Host Configuration Protocol, and the Domain Name System resolution process. Infrastructure and architectural topics include switching and virtual local area networks, routing concepts and routing table behavior including Border Gateway Protocol basics, load balancing strategies and failure modes, firewall and access control, virtual private network technologies, and container and service network communication patterns. Diagnostic and tooling skills cover connectivity testing and path analysis, process and socket inspection, packet capture and analysis, and common command line tools and utilities used for network investigation. Performance and reliability topics include latency, bandwidth and throughput, packet loss, congestion and congestion control, connection pooling, timeout and retry strategies, and approaches to optimization. Observability, monitoring, and security practices include collecting and interpreting network metrics, logs, and traces, using packet capture tools for root cause analysis, and understanding how network issues surface in distributed applications. At senior levels expect discussion of network performance tuning, capacity planning, load balancer behavior at scale, and design decisions that affect system reliability and security.

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Domain Name System Resolution and Troubleshooting

Deep understanding of the Domain Name System resolution process and the related operational concerns. Topics include the roles of recursive resolvers and authoritative name servers, zone delegation and glue records, common record types such as address records, canonical name records, mail exchange records, name server records, text records, and service records, and how time to live values affect caching and propagation. Candidates should be able to explain frequent failure modes such as misconfigured records, propagation delays, delegation mistakes, name server outages, and secure configuration problems, and demonstrate troubleshooting techniques using query tools and packet capture to trace queries and determine whether issues stem from authoritative sources, caches, transport, or configuration.

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Routing Fundamentals and Diagnostics

Core routing concepts and practical diagnostics for both control plane and data plane issues. Coverage includes static versus dynamic routing, prefix notation and classless interdomain routing, routing tables, default routes, longest prefix selection, route summarization and redistribution, and policy based routing. Candidates should understand convergence and failover behavior and be familiar with routing protocols such as Border Gateway Protocol for interdomain routing and Open Shortest Path First for intradomain routing, including path selection attributes and techniques such as local preference, autonomous system path preference, multi exit discriminator, and equal cost multipath. Diagnostic topics include traceroute analysis, route advertisement inspection, route table validation, and troubleshooting common faults like route leaks, blackholes, incorrect next hops, and aggregation errors.

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Cloud Platforms and Infrastructure

Comprehensive understanding of cloud computing platforms and core infrastructure concepts. Candidates should know service models including Infrastructure as a Service, Platform as a Service, and Software as a Service, and be familiar with major providers such as Amazon Web Services, Google Cloud Platform, and Microsoft Azure. Core technical knowledge includes compute models, storage systems, networking fundamentals such as domain name system and load balancing, virtual private networks and network segmentation, virtualization, containerization for example Docker, orchestration with Kubernetes, serverless architectures, and microservices. Candidates should be able to evaluate trade offs between managed services and self managed solutions with respect to cost, reliability, operational burden, scalability, performance, security, and vendor lock in, and reason about when to choose platform managed services versus building custom infrastructure. The topic also covers system design considerations for high availability and fault tolerance, capacity planning and autoscaling, monitoring and observability, deployment strategies, and operational practices such as infrastructure as code and continuous integration and continuous delivery. This knowledge is critical for backend engineers, site reliability engineers, and DevOps roles and is increasingly relevant across many engineering positions.

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Networking Fundamentals

Foundational knowledge of how networks operate and how to reason about network behavior. Core concepts include the TCP IP model and common protocols such as IP, TCP, UDP, DNS, and DHCP; subnetting and address allocation; routing and switching fundamentals; VLANs and layer two segmentation; NAT and private addressing; firewall and access control behavior; VPNs and tunneling; ports and application layer protocols. Candidates should also be able to apply these fundamentals to troubleshoot connectivity and performance issues at a conceptual level, explain the TCP three way handshake, congestion and retransmission causes, and reason about where problems occur in the stack.

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Software Defined Networking Concepts

Explain the principles of software defined networking and the operational and architectural implications of separating control functions from forwarding functions. Topics include centralized and distributed controller models, network virtualization and overlay networks such as virtual extensible local area network, programmability and northbound and southbound interfaces, network function virtualization, orchestration and automation, and the security and reliability trade offs introduced by moving intelligence into software layers. Interviewers assess when software defined networking improves agility and scale and where traditional hardware approaches are preferable.

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Kubernetes Architecture and Core Components

Fundamental architecture of Kubernetes and its core components: control plane design including API server, etcd distributed state store, scheduler, controller manager, and cloud controller manager; worker node components including kubelet, kube proxy, and the container runtime; core objects and abstractions such as pods, services, deployments, stateful sets, daemon sets, jobs, config maps, and secrets; cluster state management, service discovery, health checks, and self healing. Candidates should understand how components interact, data flow, failure modes, and how to design for availability and scalability at the component level.

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Network Architecture and Design

Comprehensive principles and practical patterns for designing reliable, scalable, and secure networks across enterprise, data center, and wide area environments. Covers topology choices such as spine and leaf, hub and spoke, star, mesh, ring, and hybrid topologies, and how those choices affect resilience, latency, and scalability. Includes hierarchical design patterns for access distribution and core layers, device roles such as switches, routers, and load balancers, and cloud and data center specific patterns. Details redundancy and high availability strategies including active active and active passive failover, redundancy sizing such as N plus one, failure modes, convergence behavior, and operational implications for service level agreements. Addresses capacity planning, performance trade offs, quality of service and traffic engineering, routing and switching fundamentals and routing protocol behavior, segmentation for performance and security including virtual local area networks and subnets, and placement of security controls. Emphasizes trade offs between bandwidth, latency, cost, complexity, manageability, and operational burden, and how to select topology and design patterns for different application, performance, and operational requirements.

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Cloud & Infrastructure Topics

Network Troubleshooting and Tools

AWS Compute and Networking

Infrastructure as Code Tools

Containerization and Virtualization Trade Offs

Internet Protocol Suite Basics

Network Protocols and Encapsulation

Static Routing and IP Configuration

Amazon Web Services Core Services

Cloud Infrastructure Knowledge (AWS/GCP/Azure)

Windows Service and Process Management

GCP Core Services and Architecture Basics

Network Design and Security Architecture

Azure Core Services Overview

Kubernetes and Container Orchestration Fundamentals

Link Layer Troubleshooting

Large-Scale Consumer Device Infrastructure and Operations

Network Troubleshooting and Root Cause Analysis

Cloud Architecture Fundamentals

Understanding the Company's Infrastructure Context

Networking Fundamentals and Troubleshooting

Domain Name System Resolution and Troubleshooting

Routing Fundamentals and Diagnostics

Cloud Platforms and Infrastructure

Networking Fundamentals

Software Defined Networking Concepts

Kubernetes Architecture and Core Components

Network Architecture and Design