ANSIBLE – FOR
NETWORK ENGINEER
AUTOMATING CISCO IOS CONFIGURATIONS
06-APRIL-2025
TOPOLOGY
ANSIBLE
1 ANSIBLE | By Meraj Hassan – Keep Calm & Automation On!
INTRODUCTION - WHAT IS ANSIBLE?
In today's rapidly evolving network environments, automation is no longer a luxury—it's a necessity.
Ansible, as part of Cisco's DevNet initiative, has emerged as a go-to solution for automating network
configurations due to its simplicity, agentless architecture, and robust community support.
This document explores the practical use of Ansible in configuring Cisco IOS routers, focusing on a
real-world topology where a Linux-based Ansible control node connects to a Cisco router. We’ll walk
through installation, Ansible concepts, task and role structuring, and a live configuration example.
Furthermore, we’ll briefly introduce advanced topics like Ansible Tower and DevOps integration to
provide a forward-looking view on scaling and managing automation across enterprise networks.
In modern network automation, Ansible has emerged as a powerful tool for managing network
devices. This article focuses on configuring a Cisco IOS router connected to a server using Ansible.
We'll break down the steps, provide a detailed configuration guide, and conclude with an introduction
to Ansible Tower and DevOps.
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NETWORK TOPOLOGY – ANSIBLE
A Linux server running Ansible is connected to a Cisco IOS router. The diagram below illustrates this
setup:
Components:
• Ansible Control Node (Linux Server)
• Cisco IOS Router
• SSH Connectivity between the Server and Router
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UNDERSTANDING ANSIBLE CONCEPTS
ANSIBLE DEFINITIONS:
• Playbook: YAML file that contains automation instructions.
• Inventory: File listing the network devices.
• Modules: Predefined functions used in playbooks.
• Tasks: Individual automation actions within a playbook.
• Roles: Structured directory for organizing playbooks.
BENEFITS OF USING ANSIBLE FOR NETWORK
AUTOMATION
• Agentless Architecture: No need to install any agent on Cisco devices—Ansible uses
SSH.
• Human-readable Syntax: YAML-based playbooks are easy to understand and modify.
• Scalability: Easily automate configuration across hundreds of devices.
• Repeatability: Ensure consistent configurations across environments.
• Rollback Support: Store configurations in Git and roll back if needed.
REAL-WORLD USE CASES FOR CISCO + ANSIBLE
• Mass Interface Configuration: Bring up/down interfaces across 100+ devices.
• QoS Deployment: Push consistent QoS policies using templates.
• ACL Management: Apply and manage access lists across routers.
• Backup Automation: Automatically back up Cisco configs nightly using cron jobs +
playbooks.
• Compliance Checking: Verify device configurations against security/compliance policies.
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SETTING UP ANSIBLE IN LINUX
STEP 1: UPDATE THE SYSTEM
sudo apt update && sudo apt upgrade -y # For Debian-based systems
sudo yum update -y # For RHEL-based systems
STEP 2: INSTALL ANSIBLE
sudo apt install ansible -y # Debian-based
sudo yum install ansible -y # RHEL-based
STEP 3: VERIFY INSTALLATION
ansible –version
STEP 4: CONFIGURE SSH ACCESS TO THE CISCO ROUTER
Ensure SSH is enabled on the Cisco device and that the server has password less access.
ssh-keygen -t rsa
ssh-copy-id admin@router_ip
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BREAKING DOWN ANSIBLE COMPONENTS
A. INVENTORY FILE (HOSTS.INI)
The inventory file defines groups and host-specific variables:
[routers]
router1 ansible_host=192.168.1.1 ansible_user=admin ansible_password=cisco
B. PLAYBOOK EXAMPLE (CONFIGURE_ROUTER.YML)
A playbook defines the automation tasks:
- name: Configure Cisco Router
hosts: routers
gather_facts: no
tasks:
- name: Set hostname
ios_config:
lines:
- hostname Router1
- name: Configure an Interface
ios_config:
lines:
- interface GigabitEthernet0/1
- ip address 192.168.1.2 255.255.255.0
- no shutdown
C. RUNNING THE PLAYBOOK
Use the following command:
ansible-playbook -i hosts.ini configure_router.yml
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USING TASKS AND ROLES IN ANSIBLE
WHAT IS A TASK?
A task in Ansible is a single unit of work. Tasks execute modules with specific arguments.
Example:
- name: Set hostname
ios_config:
lines:
- hostname Router1
WHAT IS A ROLE?
A role is a structured way to organize playbooks and tasks. It allows you to reuse code and manage
large configurations.
A. DEFINING TASKS (TASKS/MAIN.YML)
This is where individual tasks reside:
- name: Set hostname
ios_config:
lines:
- hostname Router1
- name: Configure an Interface
ios_config:
lines:
- interface GigabitEthernet0/1
- ip address 192.168.1.2 255.255.255.0
- no shutdown
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B. CREATING A ROLE STRUCTURE
Create a directory layout like this:
mkdir -p roles/router_config/{tasks,handlers,templates,files,vars,defaults,meta}
C. SPLITTING TASKS INTO FILES
roles/router_config/tasks/set_hostname.yml
- name: Set hostname
ios_config:
lines:
- hostname Router1
roles/router_config/tasks/configure_interface.yml
- name: Configure Interface
ios_config:
lines:
- interface GigabitEthernet0/1
- ip address 192.168.1.2 255.255.255.0
- no shutdown
roles/router_config/tasks/main.yml
- import_tasks: set_hostname.yml
- import_tasks: configure_interface.yml
D. ROLE-BASED PLAYBOOK (ROUTER_PLAYBOOK.YML)
- name: Apply Router Configuration
hosts: routers
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roles:
- router_config
E. RUNNING THE ROLE-BASED PLAYBOOK
ansible-playbook -i hosts.ini router_playbook.yml
OUTPUT VERIFICATION
LINUX SERVER OUTPUT:
PLAY [Configure Cisco Router] ************************************************
TASK [Set hostname] *******************************************************
changed: [router1]
TASK [Configure an Interface] ***********************************************
changed: [router1]
PLAY RECAP ****************************************************************
router1: ok=2 changed=2
CISCO ROUTER OUTPUT:
Router1# show running-config
hostname Router1
interface GigabitEthernet0/1
ip address 192.168.1.2 255.255.255.0
no shutdown
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BRIEF OVERVIEW OF ANSIBLE TOWER AND DEVOPS
ANSIBLE TOWER
• A web-based GUI for managing Ansible automation at scale.
• Provides centralized logging, role-based access control (RBAC), job scheduling, and workflows.
• Helps teams collaborate on automation.
• Will be explored in the next document.
DEVOPS WITH ANSIBLE
• Integrates with tools like Jenkins, GitLab CI/CD.
• Supports Infrastructure as Code (IaC).
• Enables consistent, repeatable deployments in production.
• Next document will cover pipeline creation and testing.
ADVANCE ANSIBLE CONFIGURATION
1. ANSIBLE VAULT FOR SECURE CREDENTIAL
MANAGEMENT
Securely store passwords, SNMP strings, or SSH keys.
bash
ansible-vault create secrets.yml
ansible-vault edit secrets.yml
ansible-playbook secure_config.yml --ask-vault-pass
Example vault variable:
yaml
ansible_password: !vault |
$ANSIBLE_VAULT;1.1;AES256
643165613564...
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2. TEMPLATES AND JINJA2 FOR DYNAMIC
CONFIGURATIONS
Use Jinja2 to create templates for interfaces, VLANs, etc.
TEMPLATE EXAMPLE (HOSTNAME_TEMPLATE.J2):
nginx
hostname {{ inventory_hostname }}
Playbook using template:
yaml
- name: Apply dynamic hostname
ios_config:
src: hostname_template.j2
3. ANSIBLE FACTS & GATHERED VARIABLES
While gather_facts: no is often used with network devices, Ansible can still pull facts using modules
like ios_facts.
yaml
- name: Gather facts
ios_facts:
Output includes: { Interfaces, OS version, Hostname, Memory and CPU }
TROUBLESHOOTING TIPS
• SSH Errors: Verify ansible_user, ansible_password, and ansible_connection=network_cli.
• Command Failures: Use ansible-playbook -vvv for verbose output.
• Module Not Found: Ensure ansible.netcommon and cisco.ios collections are installed:
ansible-galaxy collection install cisco.ios
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CONCLUSION
Ansible has proven to be a powerful tool for network automation, especially for configuring Cisco
devices. With its agentless architecture and simple YAML syntax, it allows network engineers to
automate tasks efficiently, reducing human error and improving consistency. This document provided
a foundational understanding—from installation to task execution and role-based structuring. We also
touched on advanced concepts like Ansible Tower and DevOps integration, which open doors to
scalable, collaborative automation workflows.
In our next installment, we’ll dive deeper into those advanced topics, equipping you with enterprise-
grade tools for managing your network infrastructure with confidence.
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