nanog mailing list archives

Re: Question about mismatch of origin ASN in parent and more specific route object


From: Jared Mauch <jared () puck nether net>
Date: Wed, 18 Sep 2019 18:55:44 -0400



On Sep 18, 2019, at 6:34 PM, Anurag Bhatia <me () anuragbhatia com> wrote:

Hello everyone


Trying to understand the case from operators here who generate IRR based filters.



Say if a given example: 

AS X originating 2001:DB8::/32 with IRR route object having AS X in the origin
AS X originating 2001:DB8::/48 with IRR route object having AS Y in the origin


Now for folks who are generating filters, will your tools filter 2001:DB8::/48 because there's a more specific IRR 
route object which says AS Y while prefix is coming from AS X? 
Or since generation is based on ASNs (as known directly or resolved via AS SETs) your tools will just generate filter 
for AS X allowing 2001:DB8::/32 (upto say /48) and won't really for mismatching route object for 2001:DB8::/48? 
  

Generally you might build the filters one of two ways:

1) with just the ASN, eg: 267 where you would build just with that origin ASN.
2) with the AS-SET, eg: AS-NETHER

This includes 2 ASNs (but could also include other things, eg: AS-AKAMAI) and those are also expanded.

- Jared

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