Re: BGP hijack?

[Nicolas VUILLERMET <nicolas () vuillermet bzh>]

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 ;)

My 2 cents,

Nicolas


On 23/10/2023 16:21, Tyler Conrad wrote:
> 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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