4 Dec
2025
4 Dec
'25
7:40 a.m.
On Thu, 4 Dec 2025 at 06:24, C. Jon Larsen via NANOG <nanog@lists.nanog.org> wrote:
strict urpf should only ever be enabled by providers when PA space is assigned, and typically thats on a static routed assignment, never a bgp session and typically never on a bgp session / peer with a customer that is multihomed, etc.
There is a variant of strict with feasible paths, basically RIB instead of FIB. However uRPF is expensive, and if you do have BGP, you hopefully have prefix-lists, then you might just as well use those prefix-lists as an ACL, which are usually zero or near zero cost. -- ++ytti