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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.

Scott Helms
Vice President of Technology
ISP Alliance, Inc. DBA ZCorum
(678) 507-5000