North American Network Operators Group

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Re: Service providers that NAT their whole network?

  • From: Philip Matthews
  • Date: Tue Apr 19 09:12:06 2005

Thanks to everyone who replied to my question about NAT usage
in service providers (see original posting below).
I got a lot of private replies, as well as those
who posted to the list.

To summarize:
It seems that there are quite a few providers who do this.
I was told of at least 24 providers in the U.S., as well as providers
in Canada, in Central America, in Europe, and in Africa which which
do this.

It was suggested by a number of people that this was quite common
on WiFi access and for data services on cell phones.
I also heard about a number of cable access providers that do this,
and its use on DSL access was mentioned a couple of times.
(Many people didn't say what access types were affected, so I don't
feel I can derive any meaningful statistics).

A number of smaller providers told me that they do it because they
simply cannot get enough routable IP addresses from their upstream

If I was to speculate, I would guess that the practice might be more
common amongst newer providers, and with newer access methods on
more established providers.

- Philip

Philip Matthews wrote:

A number of IETF documents(*) state that there are some service providers
that place a NAT box in front of their entire network, so all their
customers get private addresses rather than public address.
It is often stated that these are primarily cable-based providers.

I am trying to get a handle on how common this practice is.
No one that I have asked seems to know any provider that does this,
and a search of a few FAQs plus about an hour of Googling hasn't
turned up anything definite (but maybe I am using the wrong keywords ...).

Can anyone give me some names of providers that do this?

Can anyone point me at any documents that indicate how common
this practice is?

- Philip

(*) Some IETF documents that mention this practice:
- RFC 3489
- draft-ietf-sipping-nat-scenarios-00.txt
(now expired, but available at