Cogent announcing more specific prefixes?

Knight, Brian Brian.Knight at us.mizuho-sc.com
Thu Nov 25 22:54:08 CST 2010


We received Cyclops alerts for one of our /24's.  It claimed that the prefix
was being announced by a provider in Hong Kong.  Our alerts fired between
10:36:30 and 10:40:36 UTC today, 2010-11-25.  The longest time period that
any alert was active was 2m 58s.

All appears to be well at this moment; the prefix is not being announced by
that provider according to routeviews.org.

It is highly unusual for us to receive alerts.  We have only 5x /24 networks
being monitored.  Given that you received similar alerts less than 1.5 hr
later, I wonder if this was a systemic problem.


-Brian Knight 
Sr. Network Engineer 
Mizuho Securities USA Inc
http://www.mizuho-sc.com/ 

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> -----Original Message-----
> From: ML [mailto:ml at kenweb.org] 
> Sent: Thursday, November 25, 2010 4:26 PM
> To: nanog at nanog.org
> Subject: Cogent announcing more specific prefixes?
> 
> Anyone else get alerts from their BGP monitoring system (In my case
> Cyclops) saying Cogent briefly announced some more specific prefixes?
> 
> AS path as reported by Cyclops: 7575 46135 174 174
> 
> /20s broken into /23s
> /23s became /24s
> 
> Also saw alerts for one to one (/23 announced has /23)
> 
> All alerts had a timestamp of: 2010-11-25 12:01:12 UTC
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