📘Cisco DevNet Associate (200-901 DEVASC)

1. Why This Topic Is Important for DEVASC

As a DevNet Associate, you are expected to understand how software is developed in modern IT environments. Cisco APIs, automation scripts, network applications, and cloud integrations are built using structured development methods.

For the exam, you must be able to:

Understand what Agile, Lean, and Waterfall are
Compare their differences
Know when each method is appropriate
Understand their advantages and disadvantages
Recognize how they apply in DevOps and network automation environments

You do not need to memorize deep theory, but you must clearly understand the concepts and how they apply to IT projects.

2. Waterfall Method

What is Waterfall?

Waterfall is a traditional software development method where the project moves step-by-step in a linear sequence. One phase must be completed before the next phase begins.

Think of it as a structured pipeline with fixed stages.

Phases of Waterfall

Requirements gathering
Design
Implementation (coding)
Testing
Deployment
Maintenance

Each phase is completed fully before moving to the next.

IT Example (DevNet Context)

A company wants to develop a network monitoring application:

First, all requirements are collected.
Then full system design is created.
Then developers write all the code.
Then testing happens.
Finally, the software is deployed.

Changes are difficult once development has started.

Key Characteristics

Sequential process
Heavy documentation
Fixed scope
Changes are costly
Predictable timeline

Advantages

Easy to understand
Clear structure
Works well when requirements are stable
Good for compliance-heavy environments

Disadvantages

Not flexible
Late testing (issues found late)
Hard to change requirements
Risky if customer needs evolve

When to Use Waterfall

When requirements are clear and unlikely to change
Government or regulated IT projects
Infrastructure projects with fixed specifications

3. Agile Method

What is Agile?

Agile is an iterative and incremental software development method. Instead of building everything at once, the project is divided into small parts and delivered in cycles.

Agile focuses on:

Collaboration
Flexibility
Continuous improvement
Fast delivery

Agile is based on the Agile Manifesto, which promotes:

Individuals and interactions
Working software
Customer collaboration
Responding to change

How Agile Works

Work is divided into short cycles called iterations or sprints (usually 2–4 weeks).

Each sprint includes:

Planning
Development
Testing
Review
Feedback

After each sprint, working software is delivered.

IT Example (DevNet Context)

A team is building an API automation tool:

Sprint 1: Develop basic authentication feature.
Sprint 2: Add device configuration module.
Sprint 3: Add logging and monitoring.
Sprint 4: Improve performance.

Each sprint delivers a usable feature.

Key Characteristics

Iterative development
Small frequent releases
Continuous testing
Close collaboration
Flexible scope

Advantages

Adapts to change easily
Faster feedback
Early detection of issues
Higher customer satisfaction

Disadvantages

Less predictable timeline
Requires strong communication
Scope can expand (scope creep)
Documentation may be lighter

Popular Agile Frameworks (Basic Awareness)

You should know names like:

Scrum
Kanban

Scrum

Uses fixed-length sprints
Roles: Product Owner, Scrum Master, Development Team
Regular meetings (stand-ups)

Kanban

Continuous flow
Visual board
Limits work in progress

4. Lean Method

What is Lean?

Lean focuses on maximizing value and minimizing waste.

It originally came from manufacturing, but it is widely used in IT and software development.

Lean development focuses on:

Eliminating unnecessary work
Delivering fast
Improving continuously
Empowering teams

Lean Principles (Important for Exam)

Eliminate waste
Build quality in
Create knowledge
Deliver fast
Respect people
Optimize the whole

IT Example (DevNet Context)

In a network automation project:

Avoid writing unnecessary features.
Automate testing instead of manual testing.
Reduce waiting time between development and deployment.
Remove redundant approval steps.

Lean encourages efficiency across the whole pipeline.

Key Characteristics

Focus on efficiency
Continuous improvement
Small batch work
Fast feedback loops

Advantages

Reduced waste
Faster delivery
Better efficiency
Lower cost

Disadvantages

Requires disciplined teams
Hard to measure “waste” clearly
Needs cultural shift

5. Comparison: Agile vs Lean vs Waterfall

Feature	Waterfall	Agile	Lean
Approach	Linear	Iterative	Efficiency-focused
Flexibility	Low	High	High
Change Handling	Difficult	Easy	Encouraged
Documentation	Heavy	Moderate	Minimal but useful
Delivery	End of project	Frequent releases	Continuous flow
Testing	After development	Continuous	Continuous
Best For	Stable requirements	Changing requirements	Process optimization

6. Agile vs Waterfall (Very Important for Exam)

Waterfall	Agile
Plan everything first	Plan in small increments
One final release	Multiple small releases
Late feedback	Early and continuous feedback
High risk if wrong requirements	Lower risk due to iteration
Strict phase boundaries	Flexible phases

Exam questions often test:

Which model handles change better? → Agile
Which model is sequential? → Waterfall
Which model delivers working software frequently? → Agile

7. Agile and DevOps (DEVASC-Relevant)

DevNet focuses heavily on automation and DevOps.

Agile supports DevOps because:

Small changes
Continuous integration
Continuous testing
Continuous delivery

Modern IT teams use Agile with CI/CD pipelines to automate:

Code integration
API testing
Deployment to cloud
Network configuration updates

Waterfall does not align well with DevOps because it delays testing and release.

8. Lean and DevOps

Lean thinking supports DevOps by:

Removing manual approval bottlenecks
Automating repetitive tasks
Reducing deployment time
Optimizing end-to-end workflow

Lean + Agile together improve software delivery speed and quality.

9. When to Use Each Method (Exam Perspective)

Use Waterfall When:

Requirements are fixed
Compliance documentation is required
Large infrastructure projects

Use Agile When:

Requirements may change
Rapid innovation is needed
API or cloud application development

Use Lean When:

Process efficiency is a priority
Delivery pipeline needs optimization
Reducing operational waste

10. Key Exam Concepts to Remember

For the 200-901 DEVASC exam, remember:

Waterfall = sequential, structured
Agile = iterative, flexible, customer-focused
Lean = efficiency, waste reduction
Agile works best in modern API and DevOps environments
Waterfall works in stable and regulated projects
Lean improves workflow efficiency
Agile delivers working software in increments
Lean optimizes the entire development lifecycle

11. Quick Summary (Simple Version)

Waterfall → Build everything step-by-step, no going back easily.
Agile → Build in small parts, improve continuously.
Lean → Remove waste, deliver faster, improve process.