Network Overlay

What is a Network Overlay?

Widely adopted protocols, such as EVPN-VXLAN, use encapsulation to produce an intelligent network overlay suitable for rapid enterprise network deployment and massive scalability.

Decoupling the overlay network from the physical topology enables on-demand deployment of layer 2 and layer 3 services, irrespective of the underlay physical topology. This eliminates the cost of manually modifying the network to cater to the movement of clients and applications.

Network overlays also carry endpoint or user role information across the network without requiring all devices in the path to understand or manage the roles.

You can use different kinds of network overlays and routing/bridging protocols. One example is EVPN-VXLAN-GBP with BGP, which is used to enforce user segmentation from switch to switch.

Other kinds of network overlays and protocols include:

• L2-GRE with OTO (AP to gateway)
• L2-GRE with PAPI (switch to gateway)
• ORO-VXLAN-GBP with OTO (gateway to gateway)
• L2-VXLAN-GBP with STP (gateway to switch)

Network overlays provide:

• Scalability—A network overlay can provide greater scalability than traditional VLAN-based approaches that require extensive manual monitoring and configuration.
• Simplicity—Holistic control of the enterprise network, facilitated by the network overlay, eliminates the need for labor-intensive management of physical and virtual infrastructure.
• Speed—Using a network overlay to deploy and operate a geographically dispersed network is much faster than using manual methods, such as VLANs.

Creating and managing a network overlay can be complex, so many organizations rely on network overlay solutions. However, not all solutions are created equal. Consider the following when evaluating network overlay solutions.

1. Does the solution offer a single pane of management for all networks in your environment—campus, data center, and SD-WAN? Using multiple tools to manage different parts of the network can mitigate many of the simplicity benefits of using a network overlay.
2. Does the solution require a rip and replace of network infrastructure? Organizations often have legacy infrastructure in place. A network overlay solution that allows for flexibility in evolution provides benefits now that can be expanded later as infrastructure needs evolve.
3. Does the network overlay solution offer flexibility in network architecture design? There are many different frameworks and protocols available for network overlays; preserving flexibility to choose can improve the organization’s ability to adapt for future requirements.