## Installing PPP - alias
## Dan Langille <dan@freebsdzine.org>

This article deals with setting up PPP aliases.  This will allow other
computers to use your FreeBSD box as a gateway to your ISP.  I will 
assume that you already have PPP installed and running.  If you haven't
installed PPP yet, you may wish to read the Installing PPP section of
The FreeBSD Diary (http://www.freebsddiary.com/freebsd/ppp.htm) or
Issue #4's PPP article (/199904/features/ppp.html).

What is a gateway?

A gateway is a link to another place.  Your computer can be a gateway
to your ISP for other computers.  It's pretty darn easy to make
FreeBSD act as a gateway.  Just add the following line to your
/etc/rc.conf file:

	gateway_enable="YES"	# Set to YES if this host will be a gateway.

The easiest way to implement this change is to reboot.  You can avoid
the reboot by issuing the following command instead of rebooting:

	sysctl -w net.inet.ip.forwarding=1

But in either case, make sure you make the change to /etc/rc.conf so
that the next time you reboot, the machine acts as a gateway.

What is an alias?

An alias is another name for something.  In networking terms, it's a 
method for translating one set of IP addresses for another set. 
Aliasing is also known as Network Address Translation (NAT) and IP
Masquerading.  Most commonly, aliasing is used to convert private 
addresses on the inside of a gateway to public addresses on the 
outside of a gateway.

For more a bit information on aliasing, see the natd section of The
FreeBSD Diary (http://www.freebsddiary.com/freebsd/natd.htm), but come
back here because you don't really want natd if you have PPP.  Or so
I've been told.

Adding aliasing to your PPP setup

The reference for this section is 
http://www.freebsd.org/tutorials/ppp/ppp21.html and I suggest you read 
that first.

I added the following line to the default section of /etc/ppp/ppp.conf:

	alias enable yes

The PPP - Pedantic PPP Primer (http://www.freebsd.org/tutorials/ppp/ppp.html)
has an excellent section on Configuring Windows Systems 
(http://www.freebsd.org/tutorials/ppp/ppp22.html) to use your newly 
created gateway.

Testing the aliasing

All of these tests assume you are using another box on your network 
and not your gateway box unless otherwise specified.  I am also 
assuming you are using dial-on-demand.

The easiest way to this this setup is to use one of your other
computers and trying pinging your ISP.  Your modem should dial and the
pings should start.  If it does, you've got it right!  If you can't
try pinging from your gateway box.  If your modem dials up, then your
other machine doesn't have the gateway properly specified.  See
Configuring Windows Systems (http://www.freebsd.org/tutorials/ppp/ppp22.html).

The next step is to browse to your ISP's homepage.  If you can't do 
that, then try the same thing on your gateway box.  If it works on
your gateway box, then the other box does not have the DNS server set
correctly.  It should be set to your ISP's DNS server.  If you are
running a DNS on your gateway box, set it to that.  See Configuring
Windows Systems (http://www.freebsd.org/tutorials/ppp/ppp22.html).

If you can't browse to a website, try browsing to an IP address.  Use
nslookup to get the IP address and enter that address into the 
browser.  If that works, then it's definitely a DNS issue.  The 
machine does not have it's DNS server specified properly.  See
Configuring Windows Systems (http://www.freebsd.org/tutorials/ppp/ppp22.html).

Dan

$Id: ppp.txt,v 1.1 2000/02/16 08:07:51 jim Exp $