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Looking for an IPv6 naysayer...
I believe all the CM vendors make at least one cable modem that has an
embedded router that does NAT (Motorola SBG901, 901, 940, 941; Arris WTM552,
etc). Some MSOs may deploy more or less of those.
From: Scott Helms [mailto:khelms at ispalliance.net]
Sent: Wednesday, February 09, 2011 3:28 PM
To: George Bonser
Cc: nanog at nanog.org
Subject: Re: Looking for an IPv6 naysayer...
Comcast, like all(?) DOCSIS systems uses 10/8 or one of the other
defined non-routable blocks for cable modems, which (if its a DOCSIS
certified device) will be a bridge only and will not do NAT. If you
we're NAT'ed on a cable modem system it must have been a proprietary
system, of which there once was a ton before DOCSIS caught on, that
Comcast hadn't phased out.
I don't believe that any of the large MSO's (and none of the small ones
I know) are doing NAT on edge devices or the core at this point, however
your point is still valid since virtually all of the ADSL lines deployed
are being NAT'ed at the modem level and that means that millions of
people are being NAT'ed without a choice. That also means that a lot of
people are already going through two NAT translations since they have
plugged in a small router behind their DSL modem and both are NAT'ing
their buggy little hearts out. We also have to think about the
tremendous number of people on all kinds of networks that are
voluntarily, like me, NAT'ing through one device of their own (usually
not educated) choice.
> How many instances of 10/8 did they say they were running? I was behind
> a NAT when I had Comcast service. I am behind a NAT currently with my
> AT&T service.
> Note that the NAT was done on the "cable modem" in both cases and not
> further in to their network. That said, from my reading of some
> industry large scale NAT devices (the A10 AX series is one which I am
> familiar with), they do things such as full cone NAT so it will still
> work with many applications that might break with conventional overload
> dynamic NAT.
Vice President of Technology
ISP Alliance, Inc. DBA ZCorum