I have now the same setup as the BSNL Dias, except that I am using Slackware on the desktop that is setup as a router. iptables and pppoe packages are installed by default.
[Posted Tuesday, November 8, 2005, 0012 IST]
Phase I: Setup the GNU/Linux System (Slackware installed to hard disk)
System specification: Intel x86 (9 years old), 500 MHz, 128 MB RAM, 40 GB HDD, DAX Ethernet cards (two, Rs.300/- each).
BSNL DataOne modem RJ-11 telephone port, RJ-45 ethernet port.
I inserted the Slackware CD and changed the BIOS to boot from the CD. On boot, my hardware was detected and proceeded with the installation.
Created partitions, formatted them and continued to install Slackware to hard disk. Installation was smooth. By default, iptables support is installed in the kernel. Slackware installs lilo to hard disk. The DAX ethernet drivers used are 8139too.
Phase II: Connect to ISP
The adsl packages were installed by default. I ran adsl-setup to setup the username, password,interfaces (using eth0 to connect to the BSNL DataOne modem). A cross-overcable connects the BSNL modem ethernet port to the system's eth0 ethernet port.
I connect using:
# adsl-start eth0 <username> ... connected!
Now the GNU/Linux desktop is connected to the Internet.
Phase III: LAN setup
I bought a 8-port Compex switch from Ritchie street, costed me Rs.1350/-. The eth1 ethernet port is connected to the Compex switch using a crossover ethernet cable. All systems that connect to the switch need to use a crossover cable.
I used the following tutorial to setup NAT and IP forwarding on the GNU/Linux router system:
I run the script and my iptables and related modules are loaded, as seen from the output of lsmod.
I then set the IP address of eth1 (manually) to 10.0.0.254. We now have the LAN setup.
Phase IV: Configuring clients
I connect my IBM Thinkpad T41 laptop to one of the switch ports and configure my ethernet (eth1) as follows:
# ifconfig eth1 10.0.0.25 up
# route add default gw 10.0.0.254 eth1
My /etc/resolv.conf contains the nameservers of BSNL domain nameservers (DNS). I can use the Internet from my laptop as well as my GNU/Linux router desktop.
I have automated the adsl-start sequence so that on power-up (both the modem and the GNU/Linux router), I get connected automatically to the Internet.