Wireless Access Point

Some might ask why you would want to build a do-it-yourself (DIY) AP when a commercially available AP often meets WLAN requirements and is affordably priced. The response to that would be flexibility and customizability. With an off-the-shelf commercial box, you are stuck with the feature-sets as offered by the AP vendor. You, therefore, have to wait for them to provide firmware upgrades to access any new functionality. In a DIY solution, you always customize the feature-set on your own.

There are at least three ways by which you can build your very own Linux-based AP. For the less adventurous, a software-only solution (e.g., Hostapd) on a vanilla Linux box is available. For the slightly more adventurous, a customized firmware implementation (e.g., OpenWRT and DD-WRT) on an existing hardware platform with a supported wireless chipset is available. And for the hardcore geeks, a customized hardware and software solution (e.g., combining a Soekris or PC Engines WRAP Board with Pyramid Linux) would get your creative juices flowing.

Hostapd This section takes a look at how you can convert a Linux box into a AP using a software-based project like Hostapd (http://hostap.epitest.fi/hostapd). The author and maintainer of the Hostapd project is Jouni Malinen.

Hostapd has a very impressive list of features that can even put some commercial solutions to shame. It not only supports WPA (IEEE 802.11i/EAP/IEEE 802.1X) features but also provides support for an integrated EAP and RADIUS authentication server within the solution. The current stable version is 0.4.9 and it supports the Prism2/2.5/3, Atheros ar521x, as well as the Prism GT/Duette/Indigo wireless chipset.

After compiling and installing Hostapd from the source code tarball, the configuration of the Hostapd daemon can be controlled via its configuration file, hostapd.conf. An example of a section of the hostapd.conf configuration file is shown here to get the hostapd daemon to perform WPA authentication using the pre-shared key:

ssid=WPA-PSK macaddr acl=1

accept_mac_file=/etc/hostapd.accept deny_mac_file=/etc/hostapd.deny auth_algs=1

own_ip_addr=192.168.0.1

wpa=1

wpa passphrase=passphrase wpa_key_mgmt=WPA-PSK wpa_pairwise=TKIP CCMP

After editing hostapd.conf, we will also need to create the hostapd.accept and hostapd.deny files that contain a list of MAC addresses for wireless cards that are allowed to connect to your AP. Once the configuration files are ready, you launch hostapd in the following manner (where /etc/hostapd.conf is the location of the hostapd configuration file edited earlier):

hostapd /etc/hostapd.conf

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