FreeBSD router: Can my internet provider detect my home network?

JJB Barbish3 at
Fri Apr 9 07:00:46 PDT 2004

Your assumption is correct. For all practical purposes ISP's can not
determine that an customer is using NAT or not. But like all things
on the internet, with special custom packet interrogation focused on
an particular customer it is possible to technically determine if
that customer is using NAT.

The cost and effort for an ISP to do that is cost prohibitive when
the only result is to terminate the customers account. ISP's have
more pressing security and usage abuse matters to invest money in
than to look for home users who use NAT.

Home Lan environments using Nat are very common, so feel free to
join the rest of us who are doing it now.

-----Original Message-----
From: owner-freebsd-questions at
[mailto:owner-freebsd-questions at]On Behalf Of Rob
Sent: Friday, April 09, 2004 2:33 AM
To: freebsd-questions at
Subject: FreeBSD router: Can my internet provider detect my home


I plan to have a FreeBSD (4.9 stable) system serving as a router
between my provider and a set of my home computers connected
via a home network.

My provider does not really like this, but I don't care so much,
as long as s/he cannot detect (too easily) my home network.

My plan is to use the following setup in my rc.conf:

(with, of course, the proper options compiled into the kernel).

Is it correct, that the combination of firewall and natd divert
all requests and thus hide the home network for my provider?
Are requests from all other networked home PC's done on behalf of
the router, so that my provider will only see requests from my

Or do I need some better (firewall?) configuration for this?

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