* [#introduction Introduction]

* [#configuring_ip_forwarding Configuring IP forwarding]

** [#linux Linux]

** [#bsd_variants__including_mac_osx_ BSD variants (including MAC OSX)]

** [#windows_ Windows ]

! Introduction

So, you have this radio network thing and after playing with it for a while you come to realize that you don't really want to bridge your home network to the rest of the Melbourne Wireless community. You need to set up a router. The router will do two things for you, it gives you the control to expose the right amount of your network and it allows you to establish a firewall between yourself and the general Melbourne Wireless network. This is exactly the same as you would have for your Internet connection.  



The router may be an embedded device, a combination device (router/wireless access point), a dedicated Linux machine (old PC) or an existing machine you make dual homed by adding an additional NIC. 



Regardless of the device you are using it needs to have more than one network interface, should be able to forward packets between the interfaces and should allow you to run firewall software and a routing daemon or two. It's probably a good idea to have a dedicated machine between you own stuff and the rest of the world, usual disclaimer here. 



! Configuring IP forwarding

Most PC based operating systems support ip forwarding but it is usually not turned on. When you have a PC that has more than one network interface any you want to enable routing you need to make some simple configuration changes to get the machine forwarding packets. 



Often you have the funny situation where the machine you want to act as a router can see other machines on both subnets but machines on one subnet cannot see machines on the other - you need to enable IP forwarding. 



!! Linux

Most standard distributions support IP forwarding. you turn IP forwarding on by setting a flag in ''/proc''. This can be done using the '''sysctl''' command or by simply echoing 1 to the file. 

 

  echo "1" > /proc/net/ipv4/ip_forward

 

Alternatively use '''sysctl'''

  

  /sbin/sysctl -a  will display all configured settings

  

  /sbin/sysctl net.ipv4.ip_forward

    net.ipv4.ip_forward = 0

  

  /sbin/sysctl -w net.ipv4.ip_forward="1"

  

!! BSD variants (including MAC OSX)

Similar to Linux, use sysctl to set the ip forwarding flag. In this case the flag is ''net.inet.ip.forwarding''.

  

  /sbin/sysctl -w net.inet.ip.forwarding="1"

  

!! Windows 

In windows routing is possible through a change to a registry parameter. Open regedit and go to the entry:

  

  HKEY_LOCAL_MACHINE \SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

  

Find the entry ''IPEnableRouter'' and set to 1 (default is 0). Reboot and you should be forwarding packets.