setup your computer to be router

Setup Your Computer to be a Router

If you have two network cards or some other means of connecting to the

internet and a network card in your ubuntu computer, it can be a very

powerfull router. You can set up basic NAT, do port forwarding, set up

a proxy, and even do packet prioritization so your downloads dont

interfere with gaming! This howto will cover setting up Webmin which

will be used to configure masquerading, DHCP, and DNS servers. It also

lets you configure port forwarding. QoS (packet prioritization) will

be covered in a later guide. This guide is made using kubuntu to show

that it will work with any version of ubuntu.

Webmin

Webmin is a web based computer management tool. It is similar to the

web interface that you get from routers you buy at stores, but allows

you to control most of the computer.

To install webmin, you must first go to its website at www.webmin.com

and download the latest version in the top right. Download the tar.gz

version into your user folder.

Once the download is complete extract it to a folder for example

\usr\webmin. I extracted it into my user folder in this tutorial

because this is just a live CD so it doesn't really matter. You may

delete the tar.gz file after you extract it as it is no longer needed.

Before you install it you will want the package "libnet-ssleay-perl".

So open the terminal and run "sudo apt-get install

libnet-ssleay-perl". Now navigate to the directory the folder is (For

me it would be "cd /home/ubuntu/webmin-1.280") and then run the

command "sudo sh setup.sh".

Config file directory [/etc/webmin]:

# Leave as default, or change as you wish

Log file directory [/var/webmin]:

# Leave as default, or change as you wish

Full path to perl (default /usr/bin/perl):

# Leave as default, or change as you wish

Web server port (default 10000):

# Leave as default or change it to what ever port you want.

Login name (default admin):

# Leave as default, or change as you wish

Login password:

# Choose a password, it will not display anything while you type

Password again:

# Self explanatory

Use SSL (y/n):

# Of course 'y'

Start Webmin at boot time (y/n):

# Once agian... 'y'

It will not finnish up the installation and you will be able to login

by using localhost:port or routerip:port like http://localhost:10000

Masquerading

Masquerading is also known as NAT. To enable it, login to Webmin, go

to the networking section, and click on firewall. It will ask you to

configure it now. press "Do network address translation on external

interface:" and choose the external interface (the one that is

connected to the internet) and click on "Enable firewall at boot

time?" then click on "Setup Firewall".

Now you must add rules to your firewall to allow traffic coming from

the internal network, loopback, and traffic related to an outgoing

connection (so that you may recieve a response to your requests).

To allow traffic from the internal network, under "Incoming packets

(INPUT)" press add rule. Give the rule a comment (name) like internal

network and press the button by the "Accept" in green writing. Then

down to "Incoming interface" put equals and put your internal

interface, in the picture below it is eth0. Scroll down and press

create.

Now do the same but put lo as incoming interface.

Now you must create another rule for existing connection. Put a

comment and press accept. For incoming interface put equals and put

your external interface (eth1 for me). Scroll down to "Connection

States" and put equals and select both "Existing connection

(ESTABLISHED)" and "Related to existing (RELATED)" and press create.

Now you must drop external connections that do not meet any of the

other rules, so set the default action of "Incoming packets (INPUT)"

to drop and press the button.

Scroll down to the bottom and press apply configuration.

Now go to the System section and click "Bootup and Shutdown". Click

"Create a new bootup and shutdown action". Make the name "webmin-ipt"

without quotes, make the description whatever you please, and for

bootup commands, put "/bin/echo 1 > /proc/sys/net/ipv4/ip_forward" and

make a new line and put "/sbin/iptables-restore

/etc/webmin/firewall/iptables.save" then press create. Find the bootup

command you just created in the list and click it then press Start

Now.

Configure DHCP

In webmin, go to servers and press DHCP Server and click Module

Config.

Replace (without quotes)

DHCP server config file with "/etc/dhcp3/dhcpd.conf"

DHCP server executable with "/usr/sbin/dhcpd3"

Command to start DHCP server with "/etc/init.d/dhcp3-server start"

Command to apply configuration with "/etc/init.d/dhcp3-server restart"

Command to stop DHCP server with "/etc/init.d/dhcp3-server stop"

Path to DHCP server PID file with "/var/run/dhcp3-server/dhcpd.pid"

DHCP server lease file with "/var/lib/dhcp3/dhcpd.leases"

and press save.

Now press "Add a new subnet" and put a description of this subnet. For

network address, make it the same as the internal address but with 0

at the end, for example my internal NIC is 192.168.1.1 so I will put

192.168.1.0 for network address. For address ranges put the range of

addrseses for your DHCP server to assign. For netmask put the same as

your subnet, most are 255.255.255.0 and press create.

Once created, press the new icon that was just created with the

network address you choose under it and scroll down to the bottom and

click "Edit Client Options". Fill in Subnet mask with your subnet,

default routers and dns servers with your internal IP and broadcast

address with the internal ip but 255 at the end (for example my

internal ip is 192.168.1.1 so I will put 192.168.1.255 for broadcast)

and press save then press start server.

Your computer will now be a DHCP server, router, and DNS server. To do

port forwarding, go to the firewall settings in webmin and go to the

Network Address Translation (nat) IPTable. From there you can add