Re: How long AS-PATH policies have you used

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

On Monday, February 23rd, 2026 at 17:52, Saku Ytti via NANOG <[email protected]> wrote:

...

> I'd like to hear about operational experiences, how long AS-PATH
> policies people have successfully run and in which NOS.

...

> How many ASN can I iterate, before I become market leading and have to
> work with vendors to fix bugs?

The largest AS path filter I can find on our network, is for one of our customers. The filter is 9002 permit entries long, each entry matches 8 ASNs, so 72016 ASNs in total.

To clarify, one "entry" is matching 8 possible origin ASNs:

permit (1|2|3|4|5|6|7|8)$ any

^ 9k of those.

This is on EOS, it works fine.

...

> So I don't really need to check the prefix again, after it passed
> RPKI. AS_PATH check is equally strong.

This is exactly why we have AS path filters too. We're looking into dropping prefix filters but keeping AS path filters until such time as ASPA (or some other method) covers that part of the path filtering space, and we're also working on RFC9234 adoption right now. Prefix filters are yucky.


Cheers,
James.
-----BEGIN PGP SIGNATURE-----
Version: ProtonMail
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=3CTS
-----END PGP SIGNATURE-----

_______________________________________________
NANOG mailing list 
https://lists.nanog.org/archives/list/[email protected]/message/AEI5PLRDVP7DDGGPEY7UAHKCFVWO6ZSR/