Overlay network

Q: How deeply does Acing the CCNA Exam: Volume 2 Advanced Networking and Security cover overlay network?

Defines overlay, underlay, and fabric and identifies VXLAN and IPsec implementations, but remains high-level.

As explained in 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.

An overlay network is a virtual network of tunnels built on top of an underlying physical network, called the underlay. Together, the overlay and underlay form the fabric. section 22.2.3

Cisco SDN solutions use overlays for different operational environments:

SD-Access builds a VXLAN overlay over a physical campus-LAN underlay. section 22.2.3
SD-WAN builds IPsec tunnels over WAN underlays such as the internet, MPLS, cellular networks, or satellite. section 22.2.3 section 22.4
ACI builds a VXLAN overlay over a physical spine-leaf data-center underlay. section 22.4

Campus fabric

A campus fabric can combine physical switches as the underlay with VXLAN tunnels as the overlay; Cisco Catalyst Center functions as the SD-Access controller. section 22.2.3

How Acing the CCNA Exam: Volume 2 Advanced Networking and Security covers it

Cover of Acing the CCNA Exam: Volume 2 Advanced Networking and Security

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Also explained in

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Acing the Certified Kubernetes Administrator Exam, Second EditionA network overlay is a virtual network abstraction built on top of an existing physical network to provide connectivity between workloads or nodes.

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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.

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 2 Advanced Networking and Security. The section links point to the parts of the book it draws on.