[NTLUG:Discuss] use linux box with 3 NICs

[Mark Bickel]

> From discuss-admin at ntlug.org Mon Feb 26 10:49 CST 2001
> From: "m m" <llliiilll at hotmail.com>
> To: discuss at ntlug.org
> Date: Mon, 26 Feb 2001 16:47:26 
> Subject: [NTLUG:Discuss] use linux box with 3 NICs

> cable modem - firewall/router -|- (public)webserver
>                   |            |- mailserver
>                   |
>                   |- private network
> 
> can linux box can do firewall/router work on this configuration?
> any one give a hint (document, howto,...)
> thanks

Yes, one can definitely do this sort of thing using Linux.
If you want to roll your own using free (as in speech and beer) software
the following links should get you thinking:

http://www.linuxdoc.org/HOWTO/Firewall-HOWTO.html
http://www.linuxdoc.org/HOWTO/IP-Masquerade-HOWTO.html
http://www.smoothwall.org/
http://www.linuxrouter.org
http://www.netsys.com/firewalls/
http://www.zdnet.com/zdhelp/stories/main/0,5594,2503199,00.html
http://freshmeat.net/search/?q=firewall

In general:
 Linux 2.0 kernel series used ipfwadm for filtering
 Linux 2.2 kernel series uses ipchains for filtering
 Linux 2.4 kernel series uses ipfilter, which provides stateful inspection
  of packets, meaning that one can filter based on packet content, not just
  port number, IP address, MAC address, etc.
 IP-Masquerading provides Network Address Translation (NAT). 

There are also a number commercial linux based firewalls, ranging from
software-only distributions which make configuration easier, to network
appliances that come pre-installed and pre-configured "out of the box".

Cheers,
Mark.Bickel at ericsson.com
mbickel at firstworld.net