This is how you setup any (Prism2) wireless card on a linux machine into a (almost) fully functioning access point.

Note: Intersil's station firmware for Prism2/2.5 chipset supports a so called Host AP mode in which the firmware takes care of time critical tasks like beacon sending and frame acknowledging, but leaves other management tasks to host computer driver. Unless this support is not there in the firmware, it cannot be run as an access point. Additionally the driver should take care of the functions not managed by the firmware.

• Firstly, install a driver for the card which supports the Hostap Mode in the wireless card. You can get one such driver from http://hostap.epitest.fi/. The page also gives some details about the issues involved. Please go through the page carefully.
• Read the READMEs in the driver directory carefully.
• For the Prism2-2002-05-19.tar.gz , do go through the README.prism2. It contains a lot of points on configuring the card.
• The README files provides instructions to install the driver for different setups. The instructions are pretty simple to understand and I don't elaborate on them here.
• Once the driver is installed and the appropriate modules are copied into the appropriate directory, we now use certain tools to configure it.
• add the following line to your /etc/modules.conf : wlan0 <_tab_> hostap_xxx where xxx will be either cs, plx or pci depending on the setup.
• now add the following lines to your /etc/rc.local file :
  • ifconfig wlan0 <_your_IP> <_your_netmask_> <_your_broadcast_>
  • route add default gw <_your_gateway_>
  • iwconfig wlan0 essid <_choose_a_ssid_for_your_access_point_>
  • iwconfig wlan0 mode Master
• Bingo! You now have your PC working as an access point. Check if it is working properly by connecting it with another wireless card (on another machine) using the ssid you specified in <_choose_a_ssid_for_your_access_point_>
• Next you would like to implement a bridge using this card and another ethernet card plugged into the machine. For this purpose it is quite useful to read the http://www.tldp.org/HOWTO/BRIDGE-STP-HOWTO/index.html or a local copy of the same http://www.iitk.ac.in/LDP/HOWTO/BRIDGE-STP-HOWTO/index.html
• For this certain bridging tools are required. A module named bridge already comes with linux kernel versions 2.2 . The bridge code for 2.4 is quite stable but in 2.2 it doesn't work very well. Not to worry though. You can get the patch at http://bridge.sourceforge.net/. The site also contains some other information about bridges and 'aims to be the central resource for all things related to Layer 2 ethernet bridging with Linux'.
• If you are using kernel version 2.4 (which is most likely) then all you need are some bridge utilities which already come with certain distributions of linux. Try running the command brctl. If it does not work, then you can download these bridge utilities from http://bridge.sourceforge.net/bridge-utils/bridge-utils-0.9.5.tar.gz
• Now follow the instructions given in the README of the package and also read the above mentioned HOW-TO in detail. Soon you would have an access point running on your machine with ethernet bridging functionality as well.