Subject: Re: Setting up NAT and then a firewall...
To: Sam Carleton <>
From: Steven M. Bellovin <>
List: tech-security
Date: 07/22/2001 14:37:49
In message <>, Sam Carleton writes:
>Manuel Bouyer wrote:
>> Ha, NO ipfilter rules. ipfilter needs to be enabled for NAT to work.
>> Try 'ipf -E' to test. You may want to create a dummy /etc/ipf.conf with just
>> pass in from any to any and enable ipf in /etc/rc.conf, so that ipf -E will
>> be run at boot.
>This is very interesting.  You say that ipfilter needs to be enabled for NAT
>to work.  The rest of my ipnat.conf file is working just fine.  I have a
>number of computers behind the NetBSD machine and they CALL are able to access
>the Internet thanks to the first three lines of the ipnat.conf file.  But all
>the same I took your word for it and created a basic ipf.conf that simply has:
>pass in from any to any
>I set ipfilter=Yes in the /etc/rc.conf and rebooted.  When I ssh from the
>outside, I still end up on the NetBSD machine (future firewall).  Any more
>thoughts on what I can try?
Have you checked out the IPfilter "howto", at  (That link is
on the NetBSD documentation page.)  I seem to recall that it gave
some instructions on what to use -- not just

	pass in from any to any

but also (I think)

	pass out from any to any

		--Steve Bellovin,