Suspecious anycast prefixes

John Kristoff jtk at cymru.com
Thu May 5 11:54:48 CDT 2011


On Thu, 5 May 2011 11:48:31 -0500
"Yaoqing(Joey) Liu" <joey.liuyq at gmail.com> wrote:

> > Furthermore, that exchange prefixes may often appear to be anycast
> > is not unusual.  Those prefixes are often originated by multiple
> > disparate networks who are connected to the exchange.

> You mean that many different exchange points are using the same set of
> prefixes as anycast service in different physical locations?

No, just that you see route announcements for the exchange prefix
coming from multiple different origins and paths.  So it may appear to
be anycast, but in reality would function as if it were multihomed with
the route originating from multiple providers.  Additionally
reachability to addresses within the prefix may differ as a result of
the peering relationships from the perspective of the path taken to get
there.

John




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