Revelati

Hello everyone this is my first post and Im a bit of a newbie when it comes to dhcp and DNS routing so please bare with me I'll try and explain what I am trying to do.

I have a large area to cover with a wireless network and the connection at points away from the router is spotty at best. Instead of going out and getting a repeater to increase the range of the router I have an old laptop with an internal wireless card and a second wlan interface in the form of a USB dongle.

What I want to do is connect to my wireless router using the internal card (Intel 4965AGN) then allow other computers to connect to my laptop as though it were a wireless router through my second interface (ALFA 500mW with RTL8187 chip)
This should allow clients connecting to my laptop to be assigned an address through dhcp and be able to send queries to my ISPs dns server while also allowing me to monitor traffic and install firewalls on my laptop.

I guess this would be a subnet of a subnet that allows for internet connectivity from both subnets.

So far I have managed to get my laptop to behave as a wireless access point using a program called airbase-ng. This program puts my USB interface into monitor mode and replaces it with a tap interface called at0. I can then set an essid and encryption and all that.

My next challenge is to get my laptop to bridge the two interfaces, (not sure if bridge is the right term) I need to have it assign IP addresses in my new subnet (listening on at0) and forward DNS requests to the router (connected by wlan0). I have been trying to use dnsmasq to accomplish this but I have not been able to find much information on doing this specific kind of thing.

If anyone could point me in the right direction it would be very much appreciated.

RumbleFish

I did something similar last winter for fun.
I used some of the hints I found here
Build A Linux-Based Wireless Access Point
Build A Linux-Based Wireless Access Point (Part 2)

This of course is a very simple configuration and does not have any sort of security. But will get the job done.
If you use the DSL (Dam Small Linux) distribution you can even get it on several hundred MB worth of space. Enough for a USB stick.

You won't easily get the features of the WiFi routers on the market. Or the ease of use.
I would recommend that you purchase one of the routers that supports OpenWRT <<http://openwrt.org/>>
You will get a very small Linux distro that is easy to setup and very powerfull.