📘Cisco DevNet Associate (200-901 DEVASC)

Automation tools help engineers perform tasks such as:

Deploying infrastructure
Configuring network devices
Managing cloud resources
Automating repetitive operations
Ensuring consistent configurations

Instead of manually logging into devices or servers, engineers write code or configuration files that automation tools execute.

1. Ansible

Overview

Ansible is an open-source automation tool widely used for configuration management, application deployment, and infrastructure automation.

It is popular because it is simple and agentless, meaning no software needs to be installed on managed devices.

Ansible uses SSH, APIs, or other protocols to connect to systems and apply configurations.

Key Capabilities of Ansible

1. Configuration Management

Ansible can configure servers, network devices, and applications automatically.

Example in an IT environment:

A network administrator can use Ansible to:

Configure VLANs on multiple switches
Deploy NTP settings on routers
Configure SNMP monitoring across devices

Instead of configuring each device individually, Ansible runs a playbook and configures all devices automatically.

2. Infrastructure Automation

Ansible can automate the deployment of IT infrastructure components such as:

Virtual machines
Containers
Network services
Firewall configurations

Example:

Ansible can automatically configure:

Linux servers
Web servers
Databases
Network devices

This ensures all systems are configured the same way.

3. Application Deployment

Ansible can install and deploy applications across many servers.

Example in an IT environment:

An engineer can create an Ansible playbook that:

Installs a web server
Deploys application code
Configures environment variables
Restarts services

This ensures that every server runs the same application configuration.

4. Network Automation

Ansible supports many network platforms including Cisco devices.

It can automate:

Router configuration
Switch configuration
Firewall policies
Network validation checks

Example:

Ansible can configure:

BGP routing
VLAN creation
Interface configuration
Access control lists (ACLs)

on hundreds of network devices at once.

5. Agentless Architecture

One major capability of Ansible is that it does not require agents on managed devices.

This provides several advantages:

Easy deployment
No software installation on network devices
Reduced maintenance

Ansible simply connects using SSH or APIs.

6. Playbooks and YAML

Ansible uses playbooks written in YAML.

A playbook defines:

Tasks
Configuration changes
Automation workflows

Example tasks inside a playbook:

Configure interface
Install software
Start services

These playbooks allow automation to be version controlled and reusable.

7. Idempotency

Ansible ensures idempotent operations.

This means:

Running the same playbook multiple times will not create duplicate or conflicting configurations.

If the desired configuration already exists, Ansible will not change anything.

2. Terraform

Overview

Terraform is an Infrastructure as Code (IaC) tool used to create, manage, and provision infrastructure resources.

Terraform is widely used for cloud infrastructure automation.

Instead of manually creating cloud resources, engineers write code that describes the infrastructure.

Key Capabilities of Terraform

1. Infrastructure as Code (IaC)

Terraform allows engineers to define infrastructure using configuration files.

These files describe resources such as:

Virtual machines
Networks
Load balancers
Storage systems
Cloud services

Example in an IT environment:

A Terraform configuration can define:

A cloud network
Multiple virtual machines
Firewall rules
Storage volumes

Terraform then automatically builds the infrastructure.

2. Multi-Cloud Infrastructure Deployment

Terraform supports multiple cloud providers including:

AWS
Azure
Google Cloud
Private cloud platforms

This capability allows organizations to manage infrastructure across different platforms using a single tool.

Example:

A Terraform script could deploy:

Virtual machines in AWS
Databases in Azure
Storage in Google Cloud

All from one automation configuration.

3. Infrastructure Provisioning

Terraform provisions infrastructure resources automatically.

Provisioning tasks include:

Creating virtual machines
Configuring networks
Creating storage
Deploying load balancers

Terraform communicates with cloud provider APIs to create these resources.

4. Desired State Management

Terraform uses a desired state model.

Engineers define the desired infrastructure state in configuration files.

Terraform then compares:

Current infrastructure state
vs
Desired infrastructure state

It automatically performs actions to match the desired state.

5. Execution Planning

Terraform generates an execution plan before making changes.

The plan shows:

What resources will be created
What resources will be modified
What resources will be deleted

This allows engineers to review changes before applying them.

6. State Management

Terraform maintains a state file.

The state file keeps track of:

Created infrastructure resources
Resource relationships
Configuration changes

This state allows Terraform to update infrastructure safely.

7. Reusable Modules

Terraform supports modules, which allow reusable infrastructure configurations.

Example:

An engineer can create a reusable module for:

Deploying a standard network
Creating a secure VM
Deploying a load balancer

Modules simplify large infrastructure deployments.

3. Cisco NSO

Overview

Cisco Network Services Orchestrator is a network automation and service orchestration platform used to automate network service provisioning and configuration across multi-vendor networks.

It is designed specifically for large-scale network automation.

Key Capabilities of Cisco NSO

1. Network Service Orchestration

Cisco NSO automates the deployment of network services across multiple devices.

Examples of network services:

VPN services
MPLS services
L3 connectivity
Data center networking services

Instead of configuring each router manually, NSO deploys services automatically.

2. Multi-Vendor Device Support

Cisco NSO can manage devices from multiple vendors.

Examples:

Cisco routers
Juniper routers
Nokia networking devices
Other supported platforms

This allows automation across heterogeneous networks.

3. Model-Driven Architecture

Cisco NSO uses data models such as:

YANG models
Network service models

These models define how services and configurations should be structured.

This approach enables model-driven programmability, which is a key concept in modern network automation.

4. Transaction-Based Configuration

Cisco NSO performs atomic transactions.

This means configuration changes are applied in a safe and consistent way.

If an error occurs during configuration:

The entire transaction is rolled back
Devices return to the previous configuration

This prevents partial configuration errors.

5. Service Abstraction

Cisco NSO allows engineers to define services at a high level.

Example:

Instead of configuring:

multiple routers
multiple interfaces
routing protocols

An engineer defines a service template, and NSO automatically applies the necessary configurations to all devices.

6. Network Service Lifecycle Management

Cisco NSO manages the full lifecycle of network services, including:

Service creation
Service modification
Service deletion
Service monitoring

This capability is essential for service provider networks.

7. Integration with APIs and Automation Tools

Cisco NSO provides APIs that allow integration with:

Python automation scripts
CI/CD pipelines
Network orchestration systems

This enables automated service deployment through programmatic interfaces.

Comparison of Ansible, Terraform, and Cisco NSO

Tool	Primary Purpose	Key Use
Ansible	Configuration automation	Configure servers and network devices
Terraform	Infrastructure provisioning	Create and manage cloud infrastructure
Cisco NSO	Network service orchestration	Automate network services across devices

Example Automation Workflow in an IT Environment

An organization might use all three tools together:

Terraform provisions infrastructure:
- Creates virtual networks
- Deploys virtual machines
Ansible configures systems:
- Installs applications
- Configures operating systems
- Applies network settings
Cisco NSO deploys network services:
- Configures VPN services
- Automates routing services
- Manages network connectivity across devices

This layered automation approach helps manage large-scale infrastructure efficiently.

Key Exam Points to Remember (DEVASC)

For the Cisco DevNet Associate exam, remember:

Ansible

Agentless automation tool
Uses YAML playbooks
Automates configuration management and application deployment
Works with servers and network devices

Terraform

Infrastructure as Code tool
Creates and manages cloud infrastructure
Uses desired state configuration
Maintains state files

Cisco NSO

Network service orchestration platform
Uses YANG data models
Supports multi-vendor networks
Provides transaction-based configuration