I actually don't know what the "OBSERVED PATHS" is showing here, 35280 doesn't appear in any of them, so are they the paths "up to" 35280 ?
Presumably 'observed paths from inside 35280', but also think it's a misleading/confusing tool. From what I can see for that prefix ( 2a0d:3dc1:6789::/48 ) , origin is 4601 , paths is to 1299. ( 1299 25091 8298 4601 ) 1299 doesn't seem to have it anywhere in their LGs, but 174 sure does in Singapore and Washington, DC. Tue Mar 3 18:39:11.114 UTC BGP routing table entry for 2a0d:3dc1:6789::/48 Versions: Process bRIB/RIB SendTblVer Speaker 2021417067 2021417067 Last Modified: Feb 25 08:49:15.258 for 6d09h Paths: (1 available, best #1) Path #1: Received by speaker 0 1299 25091 8298 4601 2001:550:0:1000::261c:1d4 (metric 118081) from 2001:550:0:1000::9a36:42af (38.28.1.212) Origin IGP, metric 4294967294, localpref 100, valid, internal, best, group-best Received Path ID 0, Local Path ID 1, version 2021417067 Community: 174:10001 174:11700 174:20666 174:21100 174:22020 Originator: 38.28.1.212, Cluster list: 154.54.66.175, 154.54.136.66, 66.28.1.3, 38.28.1.123 RIPEStat has the withdrawl at 2026-03-02 15:20:08. So it seems like Cogent is where it's stuck. AS35280 presumably only has this route because AS174 is still advertising it. This ThousandEyes tool then saying 'This ASN is potentially retaining stuck routes' is kinda crap, since Cogent appears to be the actual place it's stuck. You see the same error message for any ASN that has a path from 174. On Tue, Mar 3, 2026 at 5:00 AM James Bensley via NANOG < nanog@lists.nanog.org> wrote:
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512
Hi Hank,
It is possible for routes to get stuck in the global routing table, although it is pretty rare.
The is a project called the BGP Clock, they announce prefixes, then withdraw them, and then check if they are still visible anywhere, to see if the prefixes are "stuck". It's called the BGP Clock because they encode the time in the IPv6 prefix, so each prefix is unique and you can see when it was announced (and thus how long it's been lingering in the DFZ).
F5s ASN in one that shows as potentially having this problem according to this tool: https://www.thousandeyes.com/bgp-stuck-route-observatory/?asn=35280
Note that this can't be taken as any sort of guarantee and this is just a "hint" because there are many variables at play.
I actually don't know what the "OBSERVED PATHS" is showing here, 35280 doesn't appear in any of them, so are they the paths "up to" 35280 ?
With kind regards, James. -----BEGIN PGP SIGNATURE----- Version: ProtonMail
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