Infrastructure as Code (IAC)

• Infrastructure as Code is the practice of managing and provisioning computing infrastructure through machine-readable definition files rather than physical hardware configuration or interactive configuration tools
• Treats infrastructure the same way developers treat application code - with version control, testing, and automated deployment pipelines
• Declarative approach - you define the desired end state, and the IAC tool figures out how to achieve it
• Enables idempotency - running the same configuration multiple times produces the same result without unintended side effects

Key Benefits

• Consistency - eliminates configuration drift between environments (dev, test, prod all match exactly)
• Version Control - infrastructure changes are tracked, reviewed, and can be rolled back like code
• Automation - reduces manual errors and deployment time from hours to minutes
• Documentation - the code itself serves as living documentation of the infrastructure
• Scalability - easily replicate environments or scale resources up/down programmatically

IAC Tools Comparison

Network IAC Applications

• Network Device Configuration - Use Ansible playbooks to configure switches, routers, and firewalls consistently across the enterprise
• VLAN Provisioning - Automatically create VLANs, assign ports, and configure trunks when new departments are added
• Security Policy Deployment - Push ACLs, firewall rules, and security policies to multiple devices simultaneously
• Network Monitoring Setup - Deploy SNMP configurations, logging settings, and monitoring agents programmatically

Common IAC Patterns

• Immutable Infrastructure - replace entire servers/containers rather than updating them in place (prevents configuration drift)
• Blue-Green Deployments - maintain two identical production environments, switch traffic between them for zero-downtime updates
• Infrastructure Pipelines - use CI/CD tools to test, validate, and deploy infrastructure changes automatically
• State Management - track current infrastructure state to determine what changes need to be applied

Vocabulary

• Idempotency - Property where applying an operation multiple times has the same effect as applying it once
• Configuration Drift - When deployed infrastructure gradually differs from its original configuration due to manual changes
• Declarative - Specify what the end result should look like (SQL-like approach)
• Imperative - Specify how to achieve the result step-by-step (programming-like approach)
• State File - IAC tool’s record of what infrastructure currently exists and its configuration
• Provisioning - Creating and setting up new infrastructure resources
• Orchestration - Coordinating multiple automated tasks across different systems

Notes

• Always use version control for IAC files - treat infrastructure code with the same discipline as application code
• Start small with IAC - begin by automating simple, repetitive tasks before tackling complex multi-tier applications
• Test IAC changes in non-production environments first - infrastructure mistakes can be more costly than application bugs
• State file security is critical - these files often contain sensitive information and should be stored securely (encrypted, access-controlled)
• Consider using IAC modules/templates for common patterns (standard web server, database cluster) to promote reusability
• Network teams should collaborate with DevOps teams - IAC bridges the gap between traditional networking and modern infrastructure practices
• Backup your state files - losing state can make it difficult to manage existing infrastructure through IAC tools
• Use IAC for disaster recovery planning - being able to rebuild your entire infrastructure from code dramatically reduces RTO (Recovery Time Objective)