Hello,

Because we were migrating our default table containing the DFZ into a VRF, we had a BGP session between 2 routers terminating on one side in the main table and on the other in the VRF. We had to remove the no-export from our redistribution route-map because of this private eBGP peering.

As we were concerned about reachability with transits and peerings on both sides, we tried to activate a route-leak between the main table and the newly installed VRF DFZ.

However, as a route-leak doesn't retain BGP attributes, routes started to be learned in originate from the router containing the route-leak. So there was no hijacking on the DFZ. Moreover, my route collector listening on the DFZ did not identify any hijack during the entire migration.

On the Transit and Peering side, we are subject to max-pref on the provider side, and we have a route-map in prefix-list specific to our AS + customer community.

However, we consider Route Collectors as customers, who redistribute prefixes greater than or equal to /24 or /48, minus bogons, and based on no-export, we don't send our internal routes. Except that in addition to the route leak, the no-export was removed, which let through all IGP originate routes to our customers, and route collectors.

The problem was quickly identified, we cut the route leak and stopped all transits and peering in main table to leave only the DFZ and work on the end of migration having only some LNS not configured in the good VRF, and finished the migration direction from the new VRF DFZ.

So don't rely on the Route Collector, which is updated at the whim of the various operators, but compare what's also in the DFZ before firing up the mailing lists. What's more, route collectors are not necessarily configured in the same way as standard peers, depending on the operator. This remains a mistake on our part, which has only resulted in horrors on the monitoring route collectors and not on the DFZ routes. So Route Collectors don't behave at all like transit or peering, given the lack of max pref, prefix-list or RPKI. 

But hey, it's quicker to send a flaming mail before typing your show ip route, I agree ;)

Nicolas

Thanks for the transparency, Vincent. Are you able to share how the AS-Path became mangled to begin with? I’m assuming this was some kind of route optimizer, but maybe something else going on?

On Mon, Oct 23, 2023 at 07:32 <vincent@milkywan.fr> wrote:

Hello everyone,
I'm working for MilkyWan / AS2027 and I wanted to give you some
explanations regarding this incident. Last week-end, during an upgrade
on our network configuration, it appears that some prefixes were
announced with an incorrect AS Path. Based on our analysis, none of
these routes seem to have been announced anywhere, but to some
route-collectors (RIPE RIS, BGP.Tools, Qrator, HE.net, NLNOG RING), and
therefore didn't effectively end up in the DFZ.
The issue was discovered quickly (in a few minutes) and corrected right
away.
The incident is now closed on our side; please reach out to us should
you see anything proving otherwise.

We deeply apologize for that and we can confirm it was not a BGP hijack
attempt.

Wishing you a very pleasant day.

Vincent F. for Milkywan Team

Le 2023-10-22 19:02, Olivier Benghozi a écrit :
> Same stuff (with our ASN and our prefixes) detected here, coming from
> AS2027 (Milkywan), for a short time...
>
> Le dim. 22 oct. 2023 à 17:18, Hank Nussbacher <hank@efes.iucc.ac.il>
> a écrit :
>
>> We just had every single prefix in AS378 start being announced by
>> AS2027.
>>
>> Every announcement by AS2027 is failing RPKI yet being propagated a
>> bit.
>> Is this yet another misbehaving device or an actual attack?
>
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