This feature enables Flowspec rules to be leaked from one VRF to another. When combined with the ability to apply Flowspec rules from one VRF to interfaces in another VRF, this feature makes it possible to combine rules from different source VRFs into a target VRF, and apply the target VRF’s rules on the interfaces of the source VRFs.

EOS 4.21.3F introduces support for BGP Flowspec, as defined in RFC5575 and RFC7674. The typical use case is to filter or redirect DDoS traffic on edge routers.