Re: maximum ipv4 bgp prefix length of /24 ?

[Willy Manga <mangawilly () gmail com>]

> On 11/10/2023 03:52, Delong.com wrote:
> > On Oct 10, 2023, at 13:36, Matthew Petach <mpetach () netflight com> wrote:
> > [...]
> > Owen,
> >
> > RPKI only addresses accidental hijackings.
> > It does not help prevent intentional hijackings.
>
> OK, but at least they can help limit the extent of required desegregation in combat unless I misunderstand the whole 
> MAXPREFIXLEN option.

Actually, RFC 9319 do recommend to "avoid using the maxLength attribute 
in ROAs except in some specific cases". But I recognise that this RFC is 
not yet implemented everywhere.


> > RPKI only asserts that a specific ASN must originate a prefix.  It does nothing to validate the authenticity of the 
> > origination.
>
> Nope… It ALSO asserts (or can assert) an attribute of “Maximum allowed prefix length”.
>
> E.g. if I have a ROA for AS65500 to originate 2001:db8::/32 with a “Maximum Length” attribute of /36, then any 
> advertisement (even originated by 65500) that is longer than /36 should be considered invalid.

Yes, but in that scenario any advertisements between /32 and /36 from 
that prefix originated by AS65500 are *valid* . That's why "ROAs should 
be as precise as possible, meaning they should match prefixes as 
announced in BGP" [1]

1. 
https://rpki.readthedocs.io/en/latest/rpki/securing-bgp.html#maximum-prefix-length



--
Willy Manga
@ongolaboy
https://ongola.blogspot.com/

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