Building Wireless Community Networks, Second Edition

Chapter 5. Host-Based Networking

If you want anything done well,do it yourself. This is why mostpeople laugh at their own jokes.

—Bob Edwards

An increasingly popular method for creating wireless networks is to forgo access point hardware entirely and use wireless cards directly in a host computer. The tremendous flexibility of free operating systems (such as Linux and BSD), combined with the ubiquity of inexpensive hardware, makes host-based networking the tool of choice for many large wireless projects. The added flexibility of such systems increases their complexity; if you’re not already familiar with Linux, the details of this chapter might seem daunting. If you are just getting started with wireless networking, be sure to read the previous chapter on access points to see if they’ll fit your needs.

Like a hardware access point, most useful host-based access points have at least two network interfaces: the wireless interface and one other interface. The second is typically an Ethernet device, although it can also be a modem, another radio, or any other network device. A computer can provide all of the typical access point functions, including DHCP, NAT, bridging, and MAC filtering. In addition, you have the entire suite of Linux applications and networking mechanisms at your disposal, allowing for all sorts of interesting features (including real routing, content-based packet filtering, dynamic intrusion detection, captive web portals, IPSEC tunnels, bandwidth throttling, and just ...