Technology / Networking

What Exactly is SDN?

by Jon Welling
What Exactly is SDN? picture: A
Published on August 18, 2022

Software-defined networking is the new hotness in the IT world. Okay, it's not very new, but it is widely adopted. And, software-defined networking is a godsend for those classically trained among us or prospective new techs looking to give their sanity to the cause. But what exactly is SDN? Today, we will discuss that. 

Learn More About SDN Technology

SDNs make network management, security, and efficiency far better than a traditional network. Nonetheless, this article is only the Kool-aid to get you excited about learning how to manage an SDN. If you want to learn more, CBT Nuggets has an online course for learning CCNP: Automation and Orchestration.

If you are a beginner with the concept of an SDN, you might want to enroll in an online training course that explains network orchestration concepts. Building on those concepts, CBT Nuggets also offers training for network orchestration solutions.

An Overview of Software-defined Networking

At the heart of each SDN is a software management system. This application controller manages the entire software-defined network. At its very essence, this is what makes an SDN so powerful. In this video, CBT Nuggets trainer Jeff Kish provides a high-level look at SDN.

What is Software-defined Networking?

In the classic world of network management, network administrators needed to craft careful note-taking systems. The health of the organization depended on those notes. That's because network admins were required to manually configure and administer each component in their network. There was a lot of room for mistakes and failure in that model.  There's a reason why network engineers are paid so much money. Then software-defined networks entered the scene. 

Software-defined networks are primarily software-driven. So, the software control center handles the configuration process instead of network engineers needing to manage each network component — such as routers, switches, and firewalls by hand. It's magic. 

What is the Difference Between an SDN and a Regular Network?  

In a classic network architecture, network admins needed to create routes, VLANs, and even firewall entries explicitly. Otherwise, network engineers needed to configure both the intent and the actions of the devices to make them function properly. 

In a software-defined network, network admins interact with the control software instead of each component individually. Instead of defining rules and actions, network engineers only need to define intent. The management software then defines the rules and actions to make that intent actionable. 

For instance, if a network admin wants to block all network traffic from a specific app, they would define access controls for that app in the network management software. The management software then reaches out to the firewall to configure the appropriate ACLs, heuristic rules, and so on. This all occurs in Layer 3 of the network. 

What if you need to connect multiple business locations to the same network?  The management software can do that automatically, too. It will handle creating the WAN infrastructure and orchestrating the processes required to bring the entire business network under the same fabric despite their distance from the central network core. 

Guess What? SDNs Have Multiple Layers

Ultimately SDNs live in two segmented layers. The first is the hardware layer. The hardware layer designates the underlying network communication. Otherwise, this is where things like IP routing occurs. The network admin needs to make sure each piece of hardware can communicate with each other. 

The second layer is the software layer.  This is the management control software mentioned above. The software layer includes more mechanisms, though, and this is the part that makes a software-defined network so powerful. These extra mechanisms are APIs. 

SDNs can be driven with DevOps software because of those APIs. This means that network engineers can use tools like Chef, Puppet, or Terraform to control their network. This also implies that network engineers can use both version control software and automation applications for network deployments. Pretty cool, huh?

Can You Use Any Network Equipment in a SDN?

Do you want to deploy a software-defined network? Easy enough! Pick out your preferred vendor solution and go to town. Most network equipment vendors have a variety of pre-defined product packages that fit the bill. That wasn't the original idea of an SDN, however. The software-defined network was initially meant to be universal. The goal was to be able to use products from Cisco, Ubiquiti, or Palo Alto together. The reality is that dream hasn’t come true yet. 

Vendors like Cisco are working hard to make their equipment more cross-compatible with other vendors. To a degree, many vendor solutions are already cross-compatible with newer pieces of orchestration software. Still, you'll want to use vendor hardware verified to work with your organization's requirements for the best results. 


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