Newbie x Cisco IOS-XR x ROV: BCP to not harassing peer(s)

Saku Ytti saku at
Sat May 14 07:08:58 UTC 2022

On Sat, 14 May 2022 at 00:17, Jakob Heitz (jheitz) <jheitz at> wrote:

Hey Jakob,

> 'RPKI-tested-only' will store all routes that encounter a 'validation-state' test
> in the inbound route policy. In that case, when an RPKI server updates a VRP to the
> router, it can re-run the inbound policy from the stored route and not require a
> refresh request to be sent.

> 'RPKI-dropped-only' causes the dropped routes to be stored. This will prevent
> the unnecessary route-refreshes described above. It does not prevent all
> route-refreshes, but uses significantly less memory than 'RPKI-tested-only'

I'm sorry, but I am unable to reason what these answers mean in
context of question that was:

if validation-state is valid then

I am assuming

a) RPKI-tested-only would be same normal, and keep every single route
b) RPKI-dropped-only would not keep anything (but it also might keep
everything and be same as a))

That is, in this specific scenario, as far as I understand, there is
no effect on the optimisations.

Just to clarify why this type of policy may not be insane. IOS-XR has
a 300k prefix limit for prefix-set, this limit is regularly hit by low
quality as-set. By low quality I mean almost all as-set expand to
unnecessarily large prefix-set, because as-set tend to be 'add only',
there is no incentive to remove, so they just grow over time and do
not represent in a meaningful manner the set of prefixes neighbours
might advertise.
And if we abstract what we the operators are actually doing, no one is
doing prefix filtering, what everyone does is build AS-tree, by
starting recursion from some as-set. So this AS-tree is the source of
truth, no prefixes at all, prefixes are almost incentidental. After we
have this AS-tree, we flatten it and for each element we ask for a
route object with that origin. And then send this list to routers.

Understanding what we actually do here, offers a mechanism for config
size reduction as well as a standardized way to programmatically
deploy those prefix-lists, by (ab)using RTR for this. We can fill all
gaps from IRR data that RPKI data leaves us, then send a complete set
of DFZ origins to routers, this allows us to accept only valid
prefixes. Further the as-graph we created and flattened we can
implement per-neighbour, which is trivial size compared to prefix-set

Now compiling those AS path filters are regexp may not be so cheap,
but some NOS offer cheap way to implement such AS filtering at scale:

If we do this 100% complete RTR and AS-set filter per neighbor, then
we actually have better routing security than we have in the most
canonical way, because we are enforcing origin:prefix relation, which
we are not enforcing when we dump larger and low quality prefix-sets
to routers. This makes us much less vulnerable to the low quality
as-set both in operational manner by not inflating config sizes and
cause commits to fail and by improving routing security.

> Regards,
> Jakob.
> -----Original Message-----
> From: Saku Ytti <saku at>
> Sent: Friday, May 13, 2022 12:36 AM
> To: Jakob Heitz (jheitz) <jheitz at>
> Cc: nanog at
> Subject: Re: Newbie x Cisco IOS-XR x ROV: BCP to not harassing peer(s)
> On Fri, 13 May 2022 at 00:44, Jakob Heitz (jheitz) via NANOG
> <nanog at> wrote:
> > RPKI-dropped-only
> > Saves a copy of only the routes dropped by an RPKI validation-state test in neighbor-in route-policy.
> >
> > RPKI-tested-only
> > Saves a copy of only the routes tested in an RPKI validation-state test in neighbor-in route-policy.
> What does this mean? If any term refers to validation-state, the route
> gets stored?
> Eg.
> if validation-state is valid then
>   pass
> else
>   drop
> a) Would 'RPKI-dropped-only' store everything or nothing?
> b) Would 'RPKI-tested-only' store everything?
> --
>   ++ytti


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