Ansible and Terraform Overview

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Plain-English explanation

Ansible automates configuration using playbooks (YAML) — SSH to devices, run modules (tasks), no agent on network gear. Great for pushing VLANs, ACLs, or NTP to many routers at once.

Terraform is declarative Infrastructure as Code — you describe desired resources in .tf files; Terraform providers talk to APIs and maintain state showing what exists vs what you declared.

Both reduce manual CLI — different sweet spots: Ansible excels at day-2 config; Terraform at provisioning cloud/VPN/VLAN objects via APIs.

Deep dive

Ansible components:

| Term | Role | |------|------| | Inventory | List of hosts/groups | | Playbook | Ordered plays | | Task | One module invocation | | Module | idempotent unit (ios_config, ios_vlan) | | Jinja2 | Templating variables |

Sample task (conceptual):

- name: Configure NTP
  cisco.ios.ios_config:
    lines:
      - ntp server 203.0.113.1

Terraform flow: Write config → terraform plan (preview diff) → terraform apply (execute) → state file tracks reality.

Puppet/Chef (awareness): Agent-based server automation — CCNA may mention comparatively; Ansible agentless is emphasized.

Step-by-step — when to use which

Scenario 1: Push consistent SNMP config to 100 switches nightly → Ansible playbook + Git.

Scenario 2: Provision AWS VPC + subnets via code in CI pipeline → Terraform.

Scenario 3: One-off lab VLAN on three switches → CLI or small Ansible — Terraform overkill.

Commands to know

ansible-playbook -i inventory.yml ntp.yml
ansible all -m ping -i inventory.yml

terraform init
terraform plan
terraform apply

Troubleshooting

| Issue | Tool hint | |-------|-----------| | Playbook changes not idempotent | Wrong module — use ios_config not raw command | | Terraform wants destroy/recreate | State drift — import or fix outside TF | | SSH works manually, Ansible fails | Inventory host key, become, creds vault | | Provider auth fail | API token scope or expired cert |

Version-control playbooks and .tf files — rollback is a git revert, not panic CLI.

Exam relevance

Practice checklist

• Label Ansible inventory, playbook, task, module from a sample
• Explain Terraform plan vs apply in one sentence each
• Compare Ansible push model vs Terraform declarative model
• Name one network module/use case for Ansible
• Explain why state file matters in Terraform