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Transit router - The distributed router for OVN interconnect.#

OVS + OVN 2025 Fall Conference (Prague) digest Program Core pick Prague · 19–20 November 2025

Abstract Slides Recording

Ales Musil (Red Hat), Mairtin O'Loingsigh (Red Hat)

Play the recording: Transit router - The distributed router for OVN interconnect.

  • Why: OVN interconnect (ovn-ic) previously offered only a Transit Switch; there was no simple way to route between Availability Zones. The Transit Router fills that gap as a distributed logical router spanning AZs — and it already underpins the OVN-Kubernetes Layer2 re-architecture (see the upgrade talk below).
  • What: A logical router instantiated across AZs in an ovn-ic deployment, behaving like OVN's distributed routers; new ovn-ic-nbctl verbs (tr-add, trp-add, trp-del, tr-list); per-AZ ARP learning with ARP responses flooded between AZs via specially added flows. The deck includes a full packet-level walkthrough (SNAT on the gateway router, Geneve tunnels between chassis, lr_in_ip_routing flow selection).
  • How: tr-add allocates a unique datapath tunnel key, delegates the ICSB datapath binding, and creates a router in each AZ; trp-add assigns resource allocation per AZ, creates logical router ports, and syncs port binding tunnel keys.
  • Where applicable: Multi-AZ OVN interconnect deployments, generic OVN. Open questions acknowledged: definition and synchronization of routes and route rules across the TR, and "local" TRP port semantics.