Modern networks are evolving rapidly to support cloud adoption, virtualization, automation, remote work, and stronger security postures. This section introduces cutting-edge concepts like software-defined networking (SDN), Zero Trust, and Infrastructure as Code (IaC), which are critical to managing large-scale and scalable environments

Software-Defined Network (SDN) & Software-Defined Wide Area Network (SD-WAN)

SDN (Software-Defined Networking)
Decouples the control plane (network logic) from the data plane (packet forwarding).

• Enables centralized control via software

• Ideal for large, scalable, cloud-based environments

SD-WAN (Software-Defined Wide Area Network)
Applies the SDN model to WANs, enabling optimized path selection and cost-effective WAN management.

Key Features:

• Application Aware – Routes traffic based on app priority

• Zero-Touch Provisioning – Devices auto-configure on boot

• Transport Agnostic – Works over MPLS, broadband, LTE, etc.

• Central Policy Management – Configuration from a single console

Virtual Extensible Local Area Network (VXLAN)

Extends Layer 2 networks over Layer 3 infrastructures.

• Enables Data Center Interconnect (DCI)

• Allows Layer 2 encapsulation over Layer 3, supporting cloud-scale environments

• Used in multi-tenant data centers and virtualized networks

Zero Trust Architecture (ZTA)

A security model where no user of device is inherently trusted, even inside the network.

Core Concepts:

• Policy-Based Authentication – Access determined by dynamic identity and context

• Authorization – Enforced via roles and policies

• Least Privilege Access – Users/devices get only the necessary access

• Supports continuous verification and segmentation

Secure Access Service Edge (SASE) / Security Service Edge (SSE)

• SASE combines networking and security functions into a single cloud-delivered service

• SSE focuses on the security components only

Examples of integrated tools include:

• SWG (Secure Web Gateway)

• CASB (Cloud Access Security Broker)

• ZTNA (Zero Trust Network Access)

• FWaaS (Firewall as a Service)

Used in hybrid work and multi-cloud environments.

Infrastructure as Code (IaC)

IaC allows networks and infrastructure to be defined and managed using code, improving consistency and automation.

Automation Techniques:

• Playbooks / Templates / Reusable Tasks – Standardized configuration blocks

• Configuration Drift / Compliance – Detects and corrects mismatches

• Upgrades – Scheduled or conditional

• Dynamic Inventories – Pulls current device lists for automated deployment

Source Control Benefits:

• Version Control – Tracks changes

• Central Repository – Shared, collaborative storage

• Conflict Identification – Alerts for overlapping changes

• Branching – Allows parallel development/testing

IPv6 Addressing

IPv6 was developed to solve the problem of IPv4 address exhaustion and support the growing Internet.

Key Concepts:

• Mitigating Address Exhaustion – Vast 128-bit address space

• Tunneling – Encapsulates IPv6 packets inside IPv4 (used during migration)

• Dual Stack – Runs both IPv4 and IPv6 in parallel

• NAT64 – Allows IPv6-only clients to communicate with IPv4-only servers

Exam Tips

• Understand that SDN = control/data plane separation; SD-WAN enables optimized routing across WANs

• Be ready to compare ZTA vs. SASE/SSE:

  • ZTA = security principle

  • SASE/SSE = cloud-delivered solutions

• Know that VXLAN = Layer 2 over Layer 3 for scalable data centers

• Memorize IaC benefits—especially version control, drift detection, and dynamic automation

• Expect IPv6 scenario questions—know when to apply tunneling, dual stack, or NAT64 during migration efforts