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One Tunnel Too Many: No-Overlay Mode in OVN-Kubernetes#

Open vSwitch and OVN 2026 Fall Conference digest Program Core pick 2–4 November 2026

Abstract

Riccardo Ravaioli, NVIDIA

  • Why: Directly hits the PM's BGP + datapath interests. When the fabric already provides an overlay, stacking Geneve on top wastes MTU and adds encapsulation cost — this is OVN-Kubernetes learning to be fabric-aware.
  • What: A new no-overlay mode letting the cluster default network and primary L3 ClusterUserDefinedNetworks route inter-node traffic via BGP-learned routes with no Geneve encapsulation, while OVN still handles local networking, policy, and Services. Per-network choice, so Geneve and no-overlay networks coexist in one cluster. (from abstract only)
  • How: BGP-learned routes replace the tunnel for inter-node forwarding (administrator-configured BGP or a managed full-mesh option); the talk follows a packet across nodes and covers the config choices that matter — outbound SNAT, MTU, tenant isolation. NVIDIA's DPU-based VM networking is one concrete example.
  • Where applicable: Clusters sitting on a fabric that already provides the overlay/underlay (typical DPU- or ToR-terminated environments). Joint Red Hat/NVIDIA effort; constraints around primary L3 networks and SNAT shape deployment.