This is vaguely familiar here in Toronto Canada.
(https://lists.nanog.org/archives/list/[email protected]/thread/HXXCJEIRWPUHHFL6MVTP7NKYWC7E76TE/)
Cogent will have some equal cost multipath (typically seen by me to
AS577) among say 3 transport links, and one physical link is down so out
of a subnet, every 3rd or fourth IP wont work because the BGP doesnt
know one leg is down. I would normally be able to triangulate around
the issue by varying the source IP the traceroute was done from. e.g.
if the advertised CIDR block is say 192.168.1.0/24, a traceroute with a
source addr of192.168.1.1 might fail, but 192.168.1.2 and 192.168.3
would work based on how the forwarding plan picks (typically a static
hash) which leg to punt the packet through.
---Mike
On 11/26/2025 11:59 AM, Lee Fawkes via NANOG wrote:
I've seen "grey failure" issues like this a few times with Cogent in the
south. There will be an issue on their backbone somewhere, and they'll
continue to advertise our prefixes and blackhole our traffic. Is this
because they've got some kind of setup where their control plane is
separated from their data plane, so that their iBGP peers stay up when
there's no path for the data to take to the site? Or is it a lack of
failover capacity and extreme congestion, where enough traffic is able to
get through that their iBGP sessions stay up, but best-effort customer
traffic is getting tossed on the floor?
On Tue, Nov 25, 2025 at 8:34 PM Michael J McCafferty via NANOG <
[email protected]> wrote:
Can confirm we are affected in Austin. We have pulled the plug to Cogent
until it recovers. Sent from my Galaxy
-------- Original message --------From: Robert DeVita via NANOG <
[email protected]> Date: 11/25/25 4:49 PM (GMT-08:00) To: North
American Network Operators Group <[email protected]> Cc:
[email protected], Robert DeVita <[email protected]> Subject:
Re: internet - at least texas Dear Cogent Customer,We are currently
experiencing an outage on our network. We are working to resolve this as
quickly as possible. Please for updates on this event.If you need to open
an individual ticket on this event, please e-mail [email protected]
and reference outage HD305673827.Impacted Region: Texas, USA /
MexicoOrder(s) Impacted: 1-300427262Outage Ticket: HD305673827Status:Get
Outlook for iOS<https://aka.ms/o0ukef>________________________________From:
Tim Burke via NANOG <[email protected]>Sent: Tuesday, November 25,
2025 5:25:08 PMTo: [email protected] <[email protected]>Cc:
[email protected] <[email protected]>; Tim Burke <[email protected]>Subject:
Re: internet - at least texasNo issues here in Houston or Dallas on cogent.
Not seeing any complaint volume on outages list, either. May be localized.>
On Nov 25, 2025, at 17:32, Aaron Gould via NANOG <[email protected]>
wrote:>> what in the world is going on in texas? i'm in south texas (san
antonio) and all 4 of my internet connections went way down! i disabled
cogent bgp and already looking better on my other transit links
(non-cogent)>> --> -Aaron>>
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