Re: Cox AS22773 uPRF issue - please contact off list

[Saku Ytti via NANOG <nanog () lists nanog org>]

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
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