DNS anycasting - multiple DNS servers on same subnet Vs registrar/registry policies

Stephane Bortzmeyer bortzmeyer at nic.fr
Tue May 29 10:34:51 UTC 2012

On Mon, May 28, 2012 at 06:56:29PM -0500,
 Brett Frankenberger <rbf+nanog at panix.com> wrote 
 a message of 15 lines which said:

> How does your employer know if two nameservers (two IP addresses) are
> on the same subnet?

The current heuristic for IPv4 is "belongs in the same /28" (and /64
for IPv6). Otherwise, Mark Andrews is right, we should use a BGP feed
but it would be complicated for a command-line tool.

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