======Recycling a 486 Laptop======

//9/1/2006//


I needed to bridge my wireless network to a four port switch connecting a few desktops in my basement.  This will document what I did.

**Stuff you need**

  - Laptop with PCIMCA abilities minimum two or built in ethernet.
  - Wireless card.
  - PCMCIA ethernet card if no built in ethernet.
  - Access to a Linux distribution.

**My Setup**

I have a 486 DX 100 laptop with 28mb of ram and 540mb of disk, one LinkSys 802.11b ethernet card and one Etherlink III PCMCIA ethernet 
card.  I installed debian sarge (little heavy for the 486, FreeBSD is faster) and plugged in both ether net cards.

The firewall modules are loaded by default so all that is left is configuration.

eth0 is my internal 192.168.0.0 network
eth1 is my internal 10.0.0.0 network in the basement.

Do the following:

          # /sbin/iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
          # /bin/echo 1 > /proc/sys/net/ipv4/ip_forward

This allows packets from eth1 to travel out of the eth0 interface.  I also setup my cable modem firewall to route all packets 
for 10.0.0.0 through the eth0 interface on the laptop.   I can reach any of the 10.0.0.0 network from any 192.168.0.0 network.  This
 was very easy and very simple.  You can even forward ports from the 192.168.0.0 network into the 10.0.0.0.  

          /sbin/iptables -t nat -A PREROUTING -p tcp -i eth1 -d 192.168.0.254 --dport 80 -j DNAT --to 10.0.0.254:80
          /sbin/iptables -t nat -A PREROUTING -p tcp -i eth1 -d 192.168.0.254 --dport 443 -j DNAT --to 10.0.0.254:443
          /sbin/iptables -A FORWARD -p tcp -i eth1 -d 10.0.0.254 --dport 443 -j ACCEPT
          /sbin/iptables -A FORWARD -p tcp -i eth1 -d 10.0.0.254 --dport 80 -j ACCEPT



A warning though, this bridge is wide open, any packets can get from eth0 to eth1 and vise versa.  This isn't meant to be a firewall at all.