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 docs
Document revision: 2026.07