How are operators using IRR?

How are operators using the data available in the various IRRs?

Using an example:

AS1 is your customer
AS1 has AS2, AS3 and AS4 described as customers in an IRR
Also assume AS2 has IRR data describing AS1000 and AS2000 as it's customers.

Are operators building AS path regexes such as the following automatically from IRR and applying that to your BGP sessions?


Is this
being paired with some AS path filtering?

I am a huge fan of path filtering, but I have so very little paths to
maintain that I can say so. I guess most operators to not filter paths,
and building prefix lists is more or less current practice. Just from
what I have seen so far.

I asked about best practice about building filteers from IRR data a
while ago on NANOG, but there were not really an answer.




I usually build a prefix-list gathering route objects having an origin AS
from the customer AS-SET.

I know some operators doing AS-PATH filtering and other who don't have
anything else than a max-prefix limit on the session.
In my previous job, one of my transit provider just had a max-prefix limit
of 4k and I was announcing 2K routes. Hopefully we were good enough to not
leak any unlegitimate routes on the sessions by misconfiguration.