What does SDN stand for?
SDN stands for Software-Defined Networking. Software-defined networking separates the control plane from the data plane, so the network is configured centrally through software. That makes segmentation easier to automate.
In a traditional network each switch and router decides for itself how to forward traffic. SDN separates that decision-making, the control plane, from the forwarding hardware, the data plane, and moves it to a central controller. Administrators and applications tell the controller what they want through an API, and the controller programs the devices. The network becomes something you configure, and automate, in one place instead of device by device.
SDN in practice: an example
A data center needs a new isolated segment for a test environment. Instead of logging in to twelve switches, an engineer submits one request to the SDN controller, which pushes the forwarding rules to every device on the path within seconds and removes them when the test ends.
What SDN is confused with
SDN vs SD-WAN: what is the difference?
SD-WAN applies the same idea, central software control, to the links between sites: it steers traffic across broadband, MPLS and cellular connections. SDN usually refers to the network inside a data center or campus. What SD-WAN stands for
SDN vs NFV: what is the difference?
NFV replaces dedicated appliances such as firewalls and load balancers with software running on standard servers. SDN changes how the network is controlled. They are often deployed together but are separate ideas.
Which exams cover SDN?
SDN is on the official CompTIA acronym list for two of the four exams covered here.
- CySA+ CS0-004: on the acronym list, not tied to one objective.
- Network+ N10-009: 1.0 (Networking Concepts). Listed there as “Software-defined Network”.
Each number is a CompTIA exam objective and the name in brackets is its domain. The exam puts the term in a scenario; it does not ask you to recite the expansion.
Check yourself: two practice questions
Written by CertSprint for this page. They are not taken from any exam.
1. In a software-defined network, which component decides how traffic is forwarded?
- Each switch independently
- The central controller
- The end user's PC
- The DHCP server
Show the answer
B. The central controller. SDN moves the control plane to a controller that programs the switches. The switches keep only the data plane: they forward as instructed.
2. What is the main security concern introduced by an SDN controller?
- It cannot be backed up
- It is a single point of control, so compromising it compromises the whole network
- It removes the need for firewalls
- It blocks all encrypted traffic
Show the answer
B. It is a single point of control, so compromising it compromises the whole network. Whoever controls the controller controls every device it manages. That is why access to it is tightly restricted and controllers are deployed redundantly.
Sources: RFC 7426: Software-Defined Networking (SDN): Layers and Architecture Terminology; NIST glossary: software-defined networking. The acronym and its expansion come from CompTIA's official acronym lists, linked from each exam glossary above. The explanation, example and questions are CertSprint's own, checked against these sources on 11 November 2026.