Spine-leaf underlay pattern
A spine-leaf underlay connects every leaf to every spine with equal-cost multipath Layer-3 links, providing predictable east-west bandwidth for overlays such as EVPN-VXLAN.
Key facts
- Intent: scalable non-blocking underlay
- Structure: L3 leaf-spine, ECMP
- Often paired with EVPN overlays
When to use
Data centers and large campuses needing scalable east-west capacity.
When not to use
Small sites where a simple collapsed core meets requirements at lower operational cost.
Verification
- ECMP hashing across spine uplinks
- Leaf-to-leaf latency/loss baselines
Related guides
- EVPN fabric overview — Spine-leaf EVPN-VXLAN fabric roles, fit criteria, and verification outline.
- EVPN-VXLAN technology — EVPN control plane with VXLAN data plane for scalable fabrics.
Owner: Novatelia Engineering / AEO Program. Reviewed: 2026-07-22. Doc version: 2026.07. Change log: Phase 6 technical authority pilot.
No datasheet copies, fabricated benchmarks, or unverified vendor authorizations appear in this document.