maximum ipv4 bgp prefix length of /24 ?

Wed Oct 11 05:44:46 UTC 2023

 > On 11/10/2023 03:52, Delong.com wrote:
>
>> On Oct 10, 2023, at 13:36, Matthew Petach <mpetach at 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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