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Systems & Data Center · Foundational

Spine-Leaf Architecture

A two-tier data center network topology in which every leaf switch connects to every spine switch, giving predictable, equal-cost paths.

Definition

Leaf switches connect servers and services, spines interconnect leaves, and leaves never connect to each other directly (except vPC/MC-LAG peers). Routed underlays with ECMP replace spanning tree, and capacity scales by adding spines or leaves. It is the basis of ACI, VXLAN EVPN and Juniper IP fabrics.

Example

Any server-to-server path crosses exactly leaf-spine-leaf, three hops.

Exam tip

Spine-leaf optimizes east-west traffic; the traditional three-tier core/aggregation/access model was designed for north-south traffic.

Don't confuse it with

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