Overlay network
An overlay network is a virtual network implemented through tunnels or other logical connections over an underlying physical network.
Acing the CCNA Exam: Volume 2 Advanced Networking and Security
An overlay network is a logically constructed network implemented through tunnels or other virtual connections over an underlying physical network.
- How it is used
- Explains how Cisco SDN solutions construct virtual connectivity over physical campus, WAN, and data-center networks.
- How deep it goes
- Defines overlay, underlay, and fabric and identifies VXLAN and IPsec implementations, but remains high-level.
- Examples
- Uses VXLAN campus and data-center overlays plus IPsec WAN tunnels as concrete implementations.
- What you can do after
- Evaluate Cisco fabric designs by separating their physical underlays from virtual overlays and identifying the tunnel technology used.
Read how Acing the CCNA Exam: Volume 2 Advanced Networking and Security explains overlay network →
Acing the Certified Kubernetes Administrator Exam, Second Edition
A network overlay is a virtual network abstraction built on top of an existing physical network to provide connectivity between workloads or nodes.
- How it is used
- Provides pod-to-pod connectivity across Kubernetes nodes when physical networking cannot directly allocate every pod address.
- How deep it goes
- Explains VXLAN encapsulation, CNI interfaces, DaemonSet deployment, plugin choices, and kubectl verification, but not detailed packet configuration.
- Examples
- Uses kindnet and Flannel DaemonSets, kubectl get ds -n kube-system, and running kube-flannel pods as verification artifacts.
- What you can do after
- Operate/configure a Kubernetes CNI and verify its node-level DaemonSet and pod status with kubectl.
Related concepts
- VXLANequivalent to · VXLAN is a network virtualization protocol that encapsulates Layer 2 frames within Layer 3 packets to extend virtual networks across routed infrastructure.
- network fabricpart of · A network fabric is an interconnected network architecture that provides coordinated connectivity across its participating devices and links.
- underlay networkcontrasts with · An underlay network is the foundational physical or logical network that provides connectivity for an overlay network.
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