Please note: if you are running PPP, then you don't want natd. PPP has aliasing
built in. Unfortunately, I've never used PPP, so I suggest you follow the Pedantic PPP Primer of the FreeBSD Handbook or perhaps just see the man
pages for information on -alias.
What's a gateway?
A gateway allows one computer to talk to an outside network and channel requests from
other computers. If you have more than one computer, it makes sense to have one of
them act as the gateway to your ISP. It allows all of your computers to share a
single modem. It's easy and it's cheap.
One of the best ways to create a gateway
is by using ipfw and natd (more information on natd).
ipfw is an Internet Packet Firewall (more information on
firewalls). Even though you may not want a firewall, it's the best way to
achieve a gateway.
Installation instructions
These instructions are taken directly from the FreeBSD natd manual. Please refer
to that document for further information. This section assumes that the network card
which is attached to your ISP is ed0. You should substitute your own
interface if necessary.
The following steps will get you going. However, at the end of this
section, I'll show you how to make these changes permanent.
If this is the first time you've created a new kernel, you may wish to reboot and
install that new kernel. Make sure your kernel reboots safely with no error
messages. If all you have done is the above changes, it should go very smoothly.
3. Create a gateway/firewall
Ensure your machine acts as a gateway and a firewall by including the following lines
in /etc/rc.conf:
gateway_enable=YES
firewall_enable=YES
4. Configure your interface
Make sure your network cards are already configured. Sorry, but I don't cover
that here. If you're using ppp, make sure you start ppp before
running natd.
5. Add natd to your services
Ensure the following line appears in /etc/services:
This can be added to /etc/rc.local (NOTE: /etc/rc.local is
deprecated; use /usr/local/etc/rc.d/ instead; see Starting
stuff at boot time and Starting stuff at boot time).
Remember to change ed0 to your external network card (i.e. the one that goes to
your ISP).
natd -interface ed0
7. Redirect the traffic to natd
You will need at least the following commands. Remember to change ed0
to your external network card (i.e. the one that goes to your ISP).
/sbin/ipfw -f flush
/sbin/ipfw add divert natd all from any to any via ed0
/sbin/ipfw add pass all from any to any
In order for the changes you've made to take effect, you'll need to reboot.
Things
should run smoothly now.
Making these changes permanent
These steps will ensure that natd is configured when you need to reboot.
Make
sure the following is in /etc/rc.conf. Remember to change ed0
to your external network card (i.e. the one that goes to your ISP). These lines tell
the system that you will be using natd, the interface which needs to be diverted,
and the flags which natd needs. In this case, we'll be adding our flags to a file
for ease of maintenance..
Then make sure the following is in /etc/natd.conf. Remember to change ed0
to your external network card (i.e. the one that goes to your ISP).
interface ed0
use_sockets yes
same_ports yes
The last two lines should ensure that DCC works correctly under IRC. If you are
using DHCP, you should also add the following line:
dynamic yes
If it doesn't work
If the above does not get things working for you, then please add your comments. Perhaps my
instructions are defective. I don't think so, but please tell me of any problems you
had and what you did to correct them.
