200-901 Infrastructure and Automation Practice Question
A DevOps team manages a hybrid cloud environment with on-premises Cisco Nexus switches and AWS VPCs using Terraform. They have a configuration management tool that pushes VLAN and interface configurations to the Nexus switches. Recently, they noticed that after a Terraform run that updates the AWS VPC subnets, some on-premises switches lose connectivity to the cloud. The team suspects a mismatch between the VLAN configurations on the Nexus switches and the AWS VPC subnets. They have a centralized source of truth stored in a Git repository containing YAML files for network definitions. Which action should the team take first to resolve the issue and prevent future occurrences?
⚠ Common exam trap
Many exam-takers assume the immediate fix is to restore or manually reconfigure the switches (options A or D), rather than first validating the source of truth (Git) to identify the root cause of the mismatch, which is a core DevOps principle of treating infrastructure as code.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Compare the Git repository's YAML definitions with the actual switch configurations and AWS VPC subnets, then correct any discrepancies.
The team's centralized source of truth in Git (YAML files) should be the authoritative reference for network definitions. By comparing these definitions against both the actual Nexus switch configurations and AWS VPC subnets, the team can identify and correct any drift or mismatch. This aligns with Infrastructure as Code (IaC) best practices, ensuring that all environments are synchronized from a single, version-controlled source before making any changes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Restore the Nexus switch configurations from the most recent backup.
Why it's wrong here
Restoring a backup reverts the switches to a pre-change state without reconciling them against the Git YAML definitions, so the VLAN mismatch recurs on the next run. It is tempting as fast recovery, and would be correct after an accidental device misconfiguration rather than a source-of-truth drift.
- ✗
Modify the Terraform scripts to automatically update Nexus switches when AWS VPC subnets change.
Why it's wrong here
Embedding Nexus updates inside Terraform couples the tool to devices it does not manage, bypassing the Git YAML source of truth and the existing configuration management tool. It is tempting because automated remediation feels proactive, and would be right if Terraform already owned the switch configuration lifecycle.
- ✓
Compare the Git repository's YAML definitions with the actual switch configurations and AWS VPC subnets, then correct any discrepancies.
Why this is correct
Reconciling the Git YAML source of truth against live Nexus and AWS VPC state exposes the VLAN/subnet mismatch causing connectivity loss. This satisfies the requirement to identify the drift first before applying any corrective automation.
- ✗
Manually reconfigure the VLANs on the Nexus switches to match the AWS VPC subnets.
Why it's wrong here
Manual reconfiguration fixes the immediate VLAN mismatch but leaves the Git YAML source of truth and the configuration management tool out of sync, so drift returns. It is tempting as a quick fix, and would be correct for a one-off device change outside any automated pipeline.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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