Install software

Next up we install the software onto the Pi that will act as the 'hostap' (host access point) You need internet access for this step so make sure that Ethernet connection is up!

sudo apt-get update
sudo apt-get install hostapd isc-dhcp-server


(You may need to sudo apt-get update if the Pi can't seem to get to the apt-get repositories)

(text above shows udhcpd but that doesnt work as well as isc-dhcp-server, still, the output should look similar)

Set up DHCP server


Next we will edit /etc/dhcp/dhcpd.conf, a file that sets up our DHCP server - this allows wifi connections to automatically get IP addresses, DNS, etc.

Run this command to edit the file

sudo nano /etc/dhcp/dhcpd.conf

Find the lines that say

option domain-name "example.org";
option domain-name-servers ns1.example.org, ns2.example.org;

and change them to add a # in the beginning so they say

#option domain-name "example.org";
#option domain-name-servers ns1.example.org, ns2.example.org;

Find the lines that say

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
#authoritative;

and remove the # so it says

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
authoritative;
Then scroll down to the bottom and add the following lines
subnet 192.168.42.0 netmask 255.255.255.0 {
	range 192.168.42.10 192.168.42.50;
	option broadcast-address 192.168.42.255;
	option routers 192.168.42.1;
	default-lease-time 600;
	max-lease-time 7200;
	option domain-name "local";
	option domain-name-servers 8.8.8.8, 8.8.4.4;
}
Save the file by typing in Control-X then Y then return

Run
sudo nano /etc/default/isc-dhcp-server
and scroll down to INTERFACES="" and update it to say INTERFACES="wlan0"

close and save the file

Set up wlan0 for static IP


If you happen to have wlan0 active because you set it up, run sudo ifdown wlan0
There's no harm in running it if you're not sure
Next we will set up the wlan0 connection to be static and incoming. run sudo nano /etc/network/interfaces to edit the file

Find the line auto wlan0 and add a # in front of the line, and in front of every line afterwards. If you don't have that line, just make sure it looks like the screenshot below in the end! Basically just remove any old wlan0 configuration settings, we'll be changing them up

Depending on your existing setup/distribution there might be more or less text and it may vary a little bit

Add the lines
iface wlan0 inet static
  address 192.168.42.1
  netmask 255.255.255.0

After allow-hotplug wlan0 - see below for an example of what it should look like.  Any other lines afterwards should have a # in front to disable them

Save the file (Control-X Y <return>)

Assign a static IP address to the wifi adapter by running
sudo ifconfig wlan0 192.168.42.1

Configure Access Point


Now we can configure the access point details. We will set up a password-protected network so only people with the password can connect.

Create a new file by running sudo nano /etc/hostapd/hostapd.conf

Paste the following in, you can change the text after ssid= to another name, that will be the network broadcast name. The password can be changed with the text after wpa_passphrase=
interface=wlan0
driver=rtl871xdrv
ssid=Pi_AP
hw_mode=g
channel=6
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=Raspberry
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP
If you are not using the Adafruit wifi adapters, you may have to change the driver=rtl871xdrv to say driver=nl80211 or something, we don't have tutorial support for that tho, YMMV!
Save as usual. Make sure each line has no extra spaces or tabs at the end or beginning - this file is pretty picky!

Now we will tell the Pi where to find this configuration file. Run sudo nano /etc/default/hostapd

Find the line #DAEMON_CONF="" and edit it so it says DAEMON_CONF="/etc/hostapd/hostapd.conf"
Don't forget to remove the # in front to activate it!

Then save the file

Configure Network Address Translation


Setting up NAT will allow multiple clients to connect to the WiFi and have all the data 'tunneled' through the single Ethernet IP. (But you should do it even if only one client is going to connect)

Run sudo nano /etc/sysctl.conf

Scroll to the bottom and add
net.ipv4.ip_forward=1
on a new line. Save the file. This will start IP forwarding on boot up

Also run
sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
to activate it immediately

Run the following commands to create the network translation between the ethernet port eth0 and the wifi port wlan0
sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sudo iptables -A FORWARD -i eth0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT
You can check to see whats in the tables with
sudo iptables -t nat -S
sudo iptables -S
To make this happen on reboot (so you don't have to type it every time) run

sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"
run sudo nano /etc/network/interfaces and add
up iptables-restore < /etc/iptables.ipv4.nat
to the very end


Update hostapd


Before we can run the access point software, we have to update it to a version that supports the WiFi adapter.
First get the new version by typing in

wget http://adafruit-download.s3.amazonaws.com/adafruit_hostapd_14128.zip

to download the new version (check the next section for how to compile your own updated hostapd) then

unzip adafruit_hostapd_14128.zip

to uncompress it. Move the old version out of the way with

sudo mv /usr/sbin/hostapd /usr/sbin/hostapd.ORIG

And move the new version back with

sudo mv hostapd /usr/sbin

set it up so its valid to run with

sudo chmod 755 /usr/sbin/hostapd

 

First test!


Finally we can test the access point host! Run
sudo /usr/sbin/hostapd /etc/hostapd/hostapd.conf
To manually run hostapd with our configuration file. You should see it set up and use wlan0 then you can check with another wifi computer that you see your SSID show up. If so, you have successfully set up the access point.

You can try connecting and disconnecting from the Pi_AP with the password you set before (probably Raspberry if you copied our hostapd config), debug text will display on the Pi console but you won't be able to connect through to the Ethernet connection yet.
Cancel the test by typing Control-C in the Pi console to get back to the Pi command line

Finishing up!


OK now that we know it works, time to set it up as a 'daemon' - a program that will start when the Pi boots.
Run the following commands
sudo service hostapd start
sudo service isc-dhcp-server start
you can always check the status of the host AP server and the DHCP server with
sudo service hostapd status
sudo service isc-dhcp-server status
To start the daemon services. Verify that they both start successfully (no 'failure' or 'errors')
Then to make it so it runs every time on boot
sudo update-rc.d hostapd enable
sudo update-rc.d isc-dhcp-server enable

Extra: Removing WPA-Supplicant

Depending on your distro, you may need to remove WPASupplicant. Do so by running this command:

sudo mv /usr/share/dbus-1/system-services/fi.epitest.hostap.WPASupplicant.service ~/

and then rebooting (sudo reboot)

Last updated on 2015-11-20 at 04.58.26 PM Published on 2013-06-12 at 04.30.11 PM