Spine-leaf is a -tier architecture built for east-west traffic. Every leaf connects to every spine.
Leaf switches connect to servers. Every server is hops from every other server.
Spine switches connect only to leaves. Adding capacity means adding more spines.
Benefits:
- Consistent latency with same hop count everywhere
- Easy scaling. Add leaves for servers, spines for bandwidth.
- All links active. No spanning tree blocking.
- ECMP uses every path.
Servers communicate through just hops.