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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Governance, Policy Enforcement, and Guardrails

Implementing policy as code, compliance checking, and safety mechanisms into infrastructure systems. Topics include automated cost controls, security policy enforcement, resource naming standards, tagging strategies, and preventing common misconfigurations. Discussion of balance between flexibility and governance.

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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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Cloud Basics AWS Fundamentals

Basic AWS concepts relevant to DevOps: EC2 instances, S3 storage, IAM for access control, basic networking (VPCs, security groups), and understanding how cloud services differ from on-premises infrastructure.

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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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Connectivity and User Access Troubleshooting

A combined diagnostic approach for incidents where users cannot reach resources because of either connectivity issues or account and permission problems. This includes triage steps to determine whether a failure is network related, system or service related, or related to authentication and authorization; using network and system diagnostic tools such as ping, traceroute, and domain name system lookups; checking firewall and access control lists; reviewing system and application logs; verifying user account status, group membership, and permissions; and testing access from different systems and network locations to isolate variables. Candidates should demonstrate logical fault isolation, escalation reasoning, and safe verification of account and permission state.

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Networking, VPC, and Connectivity

Deep understanding of AWS VPC architecture including subnets (public and private), route tables, Network Address Translation (NAT), internet gateways, and VPC endpoints. Knowledge of security groups and network ACLs. Understanding of VPN and AWS Direct Connect for hybrid connectivity. DNS and Route 53 routing policies.

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Network Monitoring and Observability

Covers strategies and tooling for observing network health and performance. Topics include active health checks versus passive telemetry, what to measure at interface and flow level, flow based telemetry such as NetFlow and sFlow and export formats such as Internet Protocol Flow Information Export, Simple Network Management Protocol based metrics, metrics hierarchy and granularity, retention and aggregation considerations, alerting strategy to manage signal to noise and avoid alert fatigue, dashboards and status pages, runbook and incident playbooks, topology and capacity planning, and common observability platforms and integrations such as Prometheus the Elastic stack and Splunk or cloud native alternatives. Interviews evaluate ability to design what to monitor how to collect it and how to turn telemetry into reliable operational signals.

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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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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 Service Selection and Tradeoffs

Frameworks and criteria for evaluating cloud platform services and making pragmatic architecture decisions. Coverage includes managed versus self managed offerings, choice of compute such as serverless functions versus containers versus virtual machines, storage class and database type selection, networking and regional availability, security and compliance considerations, operational burden and run book requirements, vendor lock in and portability risks, performance and latency trade offs, and cost modeling and total cost of ownership. Candidates should be able to articulate trade offs, provide examples of making service choices for real world constraints, and explain how selection affects operability and future evolution.

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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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Vendor Selection and Technology Evaluation

Approach for evaluating vendors, tools, and technology options before committing to them. Topics include defining requirements and success criteria, creating structured evaluation and scoring criteria, running proof of concept or pilot exercises, benchmarking performance and scalability, assessing total cost of ownership and ongoing operational burden, reviewing service level agreements and support/contract terms, examining vendor roadmaps and interoperability with existing systems, and planning for migration paths and vendor lock in mitigation. Applies to any technology or service selection decision (infrastructure and network hardware, cloud platforms, data and software tooling, security products, SaaS vendors, and similar), not just one domain.

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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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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 Service and Deployment Models

Comprehensive coverage of the primary cloud service and deployment choices and the decision criteria behind them. Explain Infrastructure as a Service, Platform as a Service, and Software as a Service, including responsibility boundaries, operational implications for security, patching, and management. Explain public cloud, private cloud, and hybrid cloud deployment types and the trade offs in control, isolation, scalability, cost, and compliance. Describe decision factors and example scenarios for selecting a service model or deployment type based on application characteristics such as multi tenancy, latency requirements, data sensitivity, regulatory constraints, integration with on premise systems, and team skills. Discuss vendor lock in, portability and migration implications, and how these choices affect cost, operational burden, resilience, and monitoring.

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Observability and Monitoring Architecture

Designing and architecting end to end observability and monitoring systems that scale, remain reliable under load, and do not become single points of failure. Topics include deciding which telemetry to collect and why including metrics logs traces and events, instrumentation strategies, collection models such as push versus pull, high throughput telemetry ingestion and pipeline design, time series storage and compression, aggregation and partitioning strategies, metric cardinality and retention tradeoffs, distributed tracing propagation and sampling strategies, log aggregation and secure storage, selection of storage backends and time series databases, storage tiering and cost optimization, query and dashboard performance considerations, access control and multi tenancy, integration with deployment pipelines and tooling, and design patterns for self healing telemetry pipelines. Senior level assessments include designing scalable ingestion and aggregation architectures, storage tiering and query performance optimization, cost and operational tradeoffs, and organizational impacts of observability data.

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Cloud & Infrastructure Topics

Network Troubleshooting and Tools

AWS Compute and Networking

Governance, Policy Enforcement, and Guardrails

Network Protocols and Encapsulation

Cloud Basics AWS Fundamentals

Static Routing and IP Configuration

Amazon Web Services Core Services

Cloud Infrastructure Knowledge (AWS/GCP/Azure)

Windows Service and Process Management

Connectivity and User Access Troubleshooting

Networking, VPC, and Connectivity

Network Monitoring and Observability

Network Design and Security Architecture

Network Troubleshooting and Root Cause Analysis

Cloud Service Selection and Tradeoffs

Understanding the Company's Infrastructure Context

Networking Fundamentals and Troubleshooting

Domain Name System Resolution and Troubleshooting

Vendor Selection and Technology Evaluation

Networking Fundamentals

Network Architecture and Design

Cloud Service and Deployment Models

Observability and Monitoring Architecture