Network fabric

As explained in Acing the CCNA Exam: Volume 2 Advanced Networking and Security

A network fabric is an interconnected network architecture that provides coordinated connectivity across its participating devices and links.

A network fabric combines the physical underlay and virtual overlay into one network infrastructure. The underlay is physical; the overlay is a virtual network of tunnels. section 22.2.3

Cisco applies the fabric model to several SDN solutions:

• SD-Access builds a VXLAN overlay over a physical campus-LAN underlay and uses Cisco Catalyst Center, formerly DNA Center, as its controller. section 22.2.3
• SD-WAN builds IPsec tunnels over WAN underlays including the internet, MPLS, cellular, and satellite connections. section 22.4
• ACI builds a VXLAN overlay over a physical spine-leaf underlay and uses the APIC as its controller. section 22.4

Figure 22.7 The Cisco SD-Access fabric, consisting of a physical underlay of switches and a virtual overlay of VXLAN tunnels. Cisco Catalyst Center is the SDN controller.

Use the diagram to distinguish the physical switch underlay, VXLAN tunnel overlay, and Catalyst Center controller in an SD-Access fabric. section 22.2.3

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

How deep it goes

Defines underlay and overlay, then contrasts SD-Access, SD-WAN, and ACI without detailing configuration or troubleshooting.

Examples

Uses campus VXLAN, WAN IPsec, and data-center spine-leaf VXLAN fabrics as concrete architectural examples.

What you can do after

Evaluate SDN diagrams by identifying their physical underlay, virtual overlay, and controlling platform.

How it connects

Connects underlay, overlay, VXLAN, IPsec, SDN controllers, SD-Access, SD-WAN, and ACI.

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Related concepts

• overlay networkhas part · An overlay network is a virtual network implemented through tunnels or other logical connections over an underlying physical network.
• underlay networkhas part · 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.