PLVision LTS for SONiC® – Foundation Fabric: A Pragmatic Path to a Scalable, Maintainable Data-Center Fabric

White Paper Abstract

Data center networks reach a natural transition point when platforms approach end of life, capacity requirements grow, or workload patterns shift toward heavier east-west traffic. The traditional three-tier topology becomes the constraint, but transitioning the fabric usually gets bundled with a full redesign of Layer-3 routing and security. And that’s where most projects stall.

This white paper examines PLVision LTS for SONiC® – Foundation Fabric, a validated blueprint that replaces the three-tier topology with a scalable EVPN/VXLAN leaf-spine fabric while keeping your existing centralized Layer-3 gateway, firewall, and upstream routing in place through a defined integration point. We walk through the forwarding model, a staged transition path, four customer use cases, and the tradeoffs that determine whether centralized routing is still the right fit for your traffic profile – or whether it’s time to look at the next blueprint in the series.

Contents

1. Executive Summary
   II. The Data Center Networking Challenge
   III. The Pragmatic Transition & LTS Foundation Fabric
   IV. Same-Subnet vs. Cross-Subnet Traffic
   V. Fabric Transition & Customer Use Cases
   VI. Is Foundation Fabric Right for You? Tradeoffs & Design Considerations
   VII. Evolution Path & Business Value
   VIII. Conclusion & Technical Appendix – Terminology

Key White Paper Highlights

• Why “transition the fabric” and “redesign the network” don’t have to be the same project. Platforms hit end-of-life or capacity limits well before the centralized Layer-3 gateway, firewall, and security model stop being the right fit. Foundation Fabric moves the physical topology first and connects the existing routing and security boundary through a single defined integration point.
• What Foundation Fabric actually is. A scalable EVPN/VXLAN leaf-spine underlay providing Layer-2 connectivity, paired with your existing centralized Layer-3 gateway – built on PLVision LTS for SONiC® for a qualified baseline and long-term support.
• The one distinction that decides whether it fits. Same-subnet traffic stays inside the fabric as Layer-2 traffic; cross-subnet traffic always routes through the centralized gateway. We show why that tradeoff – traffic tromboning and shared gateway capacity – is deliberate, not a flaw, and exactly when it stops being the right call.
• A staged transition, not a cutover. An eight-stage path from assess-and-validate through a demo or trial, fabric build, Layer-2 extension, gateway integration, and progressive workload migration – so racks or applications move over on their own schedule.
• Four customer profiles, four primary problems. Enterprise DC operators, colocation/hosting providers, regional cloud providers, and regional telecom/ISPs each map to a distinct driver – platform lifecycle, isolated Layer-2 services at scale, repeatable fabric design, or IP/MPLS integration.
• An evolution path that doesn’t strand your hardware. When cross-subnet traffic or gateway capacity becomes the constraint, Transition Fabric and Cloud Scale Fabric run on the same qualified hardware platforms, the same EVPN/VXLAN foundation, and the same operating model – no forced platform swap.