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Azure AZ-305 Drill: Hybrid Networking - Diagnosing ExpressRoute Connectivity Issues

Jeff Taakey
Author
Jeff Taakey
21+ Year Enterprise Architect | Multi-Cloud Architect & Strategist.
Jeff's Architecture Insights
Go beyond static exam dumps. Jeff’s Insights is engineered to cultivate the mindset of a Production-Ready Architect. We move past ‘correct answers’ to dissect the strategic trade-offs and multi-cloud patterns required to balance reliability, security, and TCO in mission-critical environments.

While preparing for the AZ-305 exam, many candidates struggle with hybrid networking diagnostics. In the enterprise world, this decision often hinges on balancing network visibility versus operational complexity. Let’s drill into a simulated migration scenario.

The Scenario
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Tailspin Technologies operates a large-scale hybrid environment connecting their on-premises datacenter with Azure via an ExpressRoute circuit. They run multiple Azure Virtual Machines (VMs) across virtual networks integrated into their corporate network. Recently, some VMs have exhibited intermittent connectivity issues, impacting business-critical applications.

To resolve this, Tailspin’s cloud operations team wants to analyze the network traffic flowing to and from the affected VMs to identify whether packets are being allowed or denied by any network security group (NSG) rules or routing policies.

Key Requirements
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The solution must provide detailed visibility into the real-time and historical network traffic flows at the VM level within Azure to troubleshoot connectivity effectively.

The Options
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  • A) Use Azure Network Watcher’s Traffic Analytics feature.
  • B) Deploy a Network Virtual Appliance (NVA) in the virtual network to inspect traffic.
  • C) Enable Azure Monitor Logs on the NSGs and analyze logs manually.
  • D) Use Azure Security Center alerts to identify network issues.

Correct Answer
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A) Use Azure Network Watcher’s Traffic Analytics feature.


The Architect’s Analysis
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Correct Answer
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Option A.

Step-by-Step Winning Logic
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Azure Network Watcher’s Traffic Analytics is designed to provide deep visibility into network flows across Azure VMs, including those connected via ExpressRoute. It offers aggregated, filtered, and searchable insights using log analytics workspaces, enabling quick identification of allowed or denied traffic without deploying additional infrastructure.

This choice supports multiple pillars of the Microsoft Well-Architected Framework:

  • Reliability: Proactively identifies network failures or misconfigurations causing VM connectivity issues.
  • Operational Excellence: Automates and centralizes network diagnostics, integrating with Azure Monitor and Azure Security Center for cohesive governance.
  • Security: Traffic Analytics integrates with NSG flow logs, preserving data residency and compliance.
  • Cost Optimization: Avoids the overhead and licensing costs of deploying third-party network appliances.
  • Performance Efficiency: Provides near real-time flow data without impacting VM workload performance.

This aligns well with Hybrid Cloud design patterns where on-premises connectivity relies on ExpressRoute circuits, emphasizing thorough network observability.

The Traps (Distractor Analysis)
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  • Why not Option B? Deploying an NVA can provide packet inspection but adds cost, complexity, and single points of failure. It is less scalable and not a first-line diagnostic tool.
  • Why not Option C? Manually parsing NSG logs is labor-intensive and lacks integrated visualization and filtering offered by Traffic Analytics.
  • Why not Option D? Azure Security Center alerts are focused broadly on security posture, not detailed packet flow analysis required for troubleshooting connectivity issues.

The Architect Blueprint
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  • Mermaid Diagram illustrating the flow of the CORRECT solution. Use Azure-appropriate colors (Blue/Purple).
graph TD OnPrem([On-Premises Network]) -->|ExpressRoute Circuit| AzureVNet[Azure Virtual Network] AzureVNet --> VM[Virtual Machines] VM --> NSG[Network Security Group] NSG -->|Flow Logs| LogAnalytics[Log Analytics Workspace] LogAnalytics --> TrafficAnalytics[Traffic Analytics Dashboard] style OnPrem fill:#FF8300,stroke:#333,color:#fff style AzureVNet fill:#0078D4,stroke:#333,color:#fff style TrafficAnalytics fill:#5C2D91,stroke:#333,color:#fff
  • Diagram Note: The network flows from on-premises through ExpressRoute into the Azure VNet and VMs, with NSG flow logs sent to Log Analytics, where Traffic Analytics provides monitoring and reporting.

The Decision Matrix (Mandatory for Associate/Expert Level)
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Option Est. Complexity Est. Monthly Cost Pros Cons
A) Azure Network Watcher Traffic Analytics Low Low - charges apply for log ingestion and retention Native Azure service, easy enablement, scalable, integrated with Azure Monitor and Security Center Cost grows with log volume, dependent on NSG flow logs enabled
B) Network Virtual Appliance (NVA) High High - licensing + infra cost Deep packet inspection, customizable policies Expensive, complex, single point of failure, additional maintenance
C) Manual NSG Log Analysis Medium Minimal No extra costs beyond storage Time-consuming, lacks visualization and aggregation features
D) Azure Security Center Alerts Low Included with Standard Pricing Broad security visibility Limited granularity for network flow troubleshooting

Real-World Practitioner Insight
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Exam Rule
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“For the exam, always pick Azure Network Watcher Traffic Analytics when you see hybrid or ExpressRoute-connected networks needing traffic flow insights.”

Real World
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“In production, Traffic Analytics is a foundational monitoring component. Many enterprises augment it with NVAs or Azure Firewall only when deeper packet inspection or complex security enforcement is warranted.”

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