How are operators using IRR?

Pierre-Yves Maunier nanog at
Thu Jan 17 12:45:32 UTC 2013

2013/1/17 ML <ml at>

> 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?
> ----
> AS1{1,}
> AS1{1,} AS2{1,}
> AS1{1,} AS3{1,}
> AS1{1,} AS2{1,} AS1000{1,}
> AS1{1,} AS2{1,} AS2000{1,}
> ----
> I would imagine most operators that are building policy from IRR are
> building prefix lists to limit what they are accepting.  Is this being
> paired with some AS path filtering?
> Are operators just traversing an AS-SET as far as it will go and building
> prefix lists to represent all intended prefixes to be heard on a session
> regardless of who originates them? Is the possibility of AS1000 hijacking
> AS2000 prefixes towards AS2 a problem you as the upstream to AS1 need to
> consider? (Last question assumes AS2 made a mistake and wasn't filtering
> properly on it's own customers and AS1 is just accepting all prefixes under
> the cone of AS2)
> Thanks


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.


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