What is a Network Overlay?
What is a network overlay?
Why consider a network overlay?
Digital acceleration driven by hybrid work, new customer and user experiences, and the need for improved IT efficiencies makes it more important than ever for the network to provide necessary flexibility and security to keep up with constantly changing business requirements. Advancing critical business initiatives while managing a growing volume of network sites and topologies can quickly become overwhelming. By using a network overlay, network and security administrators can configure disparate and dispersed infrastructure using a common set of services — no hands-on configuring of the underlying infrastructure required.
How a network overlay works
An overlay is a method of defining layers of network abstraction using software to run multiple separate, virtualized networks on top of a physical layer. Network overlays provide the ability to deploy flexible services based on ever-changing connectivity and mobility demands of the endpoints and applications.
将覆盖网络与物理拓扑结合在一起，可以使第2层和第3层服务的按需部署，无论底层物理拓扑如何。这消除了手动修改网络以迎合客户和应用程序移动的成本。
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.
Options for a network overlay
You can use different kinds of network overlays and routing/bridging protocols. One example isEVPN-VXLAN-GBPwith BGP, which is used from switch to switch to enforce user segmentation.
其他类型的网络叠加层和协议包括：
- L2-GRE with OTO (AP to gateway)
- L2-GRE with PAPI (switch to gateway)
- 带有OTO的Oro-Vxlan-GBP（通往网关的网关）
- L2-VXLAN-GBP with STP (gateway to switch)
网络覆盖有什么好处？
网络叠加层提供：
- 可伸缩性— A network overlay can provide greater scalability than traditional VLAN-based approaches that require extensive manual monitoring and configuration.
- 简单— Holistic control of the enterprise network, facilitated by the network overlay, eliminates the need for labor-intensive management of physical and virtual infrastructure.
- Speed- 使用网络叠加来部署和操作地理分散网络的速度要比使用手动方法（例如VLAN）快得多。
Questions to ask when selecting a network overlay solution
创建和管理网络覆盖可能很复杂，因此许多组织依赖网络覆盖解决方案。但是，并非所有解决方案都是平等的。评估网络覆盖解决方案时考虑以下内容。
- 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.
- 解决方案是否需要撕裂并替换网络基础架构？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.
- 网络覆盖解决方案是否在网络体系结构设计中提供灵活性？网络叠加有许多不同的框架和协议。保留选择灵活性可以提高组织适应未来需求的能力。
Related resources
