Security gain from NAT (was: Re: Cool IPv6 Stuff)

Jim Shankland nanog at
Mon Jun 4 18:32:39 UTC 2007

Owen DeLong <owen at> writes:
> There's no security gain from not having real IPs on machines.
> Any belief that there is results from a lack of understanding.

This is one of those assertions that gets repeated so often people
are liable to start believing it's true :-).

*No* security gain?  No protection against port scans from Bucharest?
No protection for a machine that is used in practice only on the
local, office LAN?  Or to access a single, corporate Web site?

Shall I do the experiment again where I set up a Linux box
at an RFC1918 address, behind a NAT device, publish the root
password of the Linux box and its RFC1918 address, and invite
all comers to prove me wrong by showing evidence that they've
successfully logged into the Linux box?  When I last did this,
I got a handful of emails, some quite snide, suggesting I was
some combination of ignorant, stupid, and reckless; the Linux
box for some reason remained unmolested.

Jim Shankland

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