Deep ThoughtsBlog
← Back to all writing

Network+ Exam

Software defined networking

October 29, 2025

  • #network+

Software defined networking

Approach to networking that uses software based controllers or APIs to communicate with underlying hardware infrastructure and direct traffic on a network.

Allows the network to make smart descisions based on the application it’s working to support. allows to easially manage network traffic which cn help with scalabiility

iac INFRASTRUCUTE AS COD

includes the provisioning of archiceture in which deployment of resources is performed by scriped utomation and orchestration.

Control plane - carries the trafic tha tprovides the signals to and from a router. across multiple media types makes descisions how traffic is prioritized. decides where to go

data plane - used to carrie user traffic on the network. moves the data

management plane - used to administer the routers and switches and monitors traffic condictions and the sttus of the network.

use an SDN applicstion to define the policy descisions. flexibility

speed and agility

automaton - full deployment with orchestrtion.

critical when dealing with high availability and volitiy. networks

single point of failure

high vulneravility

open SDN - open source variant that relies on open ource

hybrid SDN network that employs traditional SDN protols to operate itself

SDN overlay - create network abstractin to run multiple fvirtualized networks

f

Software Defined Networking (SDN)

Concept

  • Approach to networking using software controllers or APIs to manage and direct traffic.
  • Separates the decision-making from the hardware.
  • Enables automation, agility, and scalability.

SDN Planes

  1. Control Plane
    • Makes decisions on how traffic should flow (routing, prioritization, QoS).
    • “Brains” of the network.
  2. Data Plane
    • Forwards actual user traffic based on control plane instructions.
    • “Muscle” of the network.
  3. Management Plane
    • Used by admins to configure devices, monitor status, and push policies.
    • Provides visibility into network health.

Features

  • Policy-driven control: Use SDN apps to define traffic priorities.
  • Automation & Orchestration: Infrastructure as Code (IaC) for fast provisioning.
  • Agility & Flexibility: Networks adapt quickly to app needs.
  • Overlay Networks: Abstract multiple virtualized networks over physical infrastructure.

Deployment Models

  • Open SDN: Open-source variant, uses open standards (e.g., OpenFlow).
  • Hybrid SDN: Combines traditional networking with SDN protocols.
  • SDN Overlay: Creates network abstractions (e.g., virtual networks on top of existing hardware).

Pros

  • Scalability (easy traffic management).
  • Speed (policy and automation driven).
  • Centralized control (one dashboard).

Cons

  • Single Point of Failure: If the controller fails, the whole network may fail.
  • Security Risks: Centralized control plane is a high-value target.
  • Complexity of setup and integration.

✅ Exam Must-Knows

  • SDN separates control plane (decisions) and data plane (traffic forwarding).
  • Uses software controllers and APIs.
  • Benefits: scalability, agility, automation.
  • Risks: single point of failure, vulnerabilities in centralized control.
  • Types: Open, Hybrid, Overlay.

⚡Memory Trick:

Think: SDN = Software Directs Networking.