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Date:      Sat, 08 Jul 2000 17:27:52 -0400
From:      Jim Durham <durham@w2xo.pgh.pa.us>
To:        Stuart Rogers <srogers@cableregina.com>
Cc:        freebsd-security@FreeBSD.ORG
Subject:   Re: Firewall help
Message-ID:  <39679CD8.ECF9A7D0@w2xo.pgh.pa.us>
References:  <000501bfe857$aa912160$23144818@cableregina.com>

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Stuart Rogers wrote:
> 
>     Yes hello. I'm a newer BSD user and have freebsd 3.3 powerpak. I run a
> small intranet and have my systems hooked up to a cable modem. I want to
> make an old 486 box into a basic firewall. I'm not running any servers off
> the cable modem I just want to protect against people getting into my
> system. Does anyone know of the best way to go about this. All sugestions
> and comments would be apreciated.
> 
>                                                                 Stuart
> Rogers

I do something of the same sort here. I am on DSL, not cable, but
the input/output of my DSL modem is ethernet, as are cable modems.

You need an old '486 with two ethernet cards. I'll probably miss
something,
but here is the gist of setting it up:

Let's say your two cards are "ed0" and "ed1" and that you want to use
the 10. network on your LAN. Lets say the cable company assigned you
the IP address YOUR_IP and the gateway YOUR_GATEWAY and the netmask
YOUR-NETMASK Let's say the cable modem plugs into ed0 and the LAN
hub is on ed1.

In /etc/rc.conf:

ifconfig_ed0="inet  YOUR_IP netmask YOUR_NETMASK"
defaultrouter="YOUR_ROUTER"
ifconfig_ed1="10.0.0.1 netmask 255.255.255.0"
named_enable="YES"
firewall_enable="YES"
firewall_type="simple"
firewall_quiet="NO"
natd_enable="YES"
natd_interface="ed0"
network_interfaces="lo0 ed0 ed1"

In /etc/rc.firewall, section "simple":

oif="ed0"
onet="YOUR_IP with "O" as last octet"
omask="YOUR_NETMASK"
oip=YOUR_IP

iif="ed1"
inet="10.0.0.0"
imask="255.255.255.0"
iip"10.0.0.1"

Compile a new kernel. add options "IP_DIVERT" and "IP_FIREWALL"
Assign IPs of 10.0.0.2 and up to your LAN computers.

I probably missed something, but that's most of it.
- 
Jim Durham


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