Starting with OVN 25.03, OVN supports the "dynamic-routing-redistribute" option on logical routers/logical router ports.  Through this configuration users can specify whether OVN should advertise (install routes) into a Linux VRF attached to the configured logical router.

Currently any combination (comma-separated) of the following values is supported:

• "connected" - advertise logical router port networks
• "connected-as-host" - advertise all IPs owned by a logical router (and connected logical switches and their ports) as host routes (/32 or /128)
• "static" - advertise all static routes configured on the logical router
• "lb" - advertise VIPs of load balancer configured on the router or adjacent logical routers
• "nat" - advertise all SNAT and DNAT_and_SNAT IPs configured on the router or adjacent logical routers

In the current implementation "distributed" DNAT_and_SNAT IPs are advertised from all chassis for which the logical router datapath is considered local (workloads of connected to the router are reachable through OVN from the chassis).

A "distributed" DNAT_and_SNAT rule is configured by specifying all of the following:

• external IP
• internal IP
• mac address to be used as source after SNAT
• logical switch port, "LSP",  of the workload behind NAT

OVN's implementation advertises routes for such NAT IPs on all chassis that consider the logical router datapath as "local".  There is a distinction though:

1. on the chassis where "LSP" is bound (on the chassis where the workload is running) the route is advertised with a better metric
2. on the chassis where the "LSP" is NOT bound the route is advertised with a worse metric

The reason this has been chosen as implementation was to provide a level of redundancy at OVN level (through the overlay).

However, in specific deployments (e.g., with the fabric consisting of a spine-leaf topology), this is not necessary and actually can affect optimal routing of packets in the fabric.

The goal of this feature is to export a configuration option to the user that would allow users to choose to not advertise the route on chassis where the workload isn't running ("2" above).

A potential way to configure this would be to add a new supported value for the dynamic-routing-redistribute option, e.g., "nat-local".