Usurping the BTHomeHub with a Raspberry Pi: Part 1

Ben Tasker

2014-01-19 07:34 (updated 2019-05-06 10:36)

I used to run a nice pfSense box as my router, unfortunately power bills being what they are, I reverted back to using a BTHomeHub. Unfortunately, the BTHomeHub isn't particularly good - the Wifi signal sucks, it's DNS server seems to daydream and it occasionally forgets that it should be assigning some devices the same IP every time (or more precisely, will give their IP away if they are not currently present).

We could, of course, replace the HomeHub with something a bit more up market, but where's the fun in that? In this post, we'll be starting down the route of using a Raspberry Pi to usurp some of the power the BTHomeHub currently holds over the LAN. Eventually, the HH will be acting as nothing but a dumb internet gateway, doing a little bit of NAT and not much else.

Getting the Kit

It should go without saying that we'll be needed a Model B Raspberry Pi, a case (homemade or otherwise), and an SD Card. As we're planning on taking away the HomeHub's WLAN responsibilities we'll also want a USB wireless dongle - I've found the Edimax EW-7711USn USB 802.11 b/g/n Adaptor plays rather well with the Pi, especially as you can unscrew the antenna and add something really high gain if needed.

Getting Started

So the first thing we need to do, is to install our Base OS. We're going to be using Raspbian, so download an image from RaspberryPi.org, and write the image to your SD card

sudo dd if=2013-12-20-wheezy-raspbian.img of=/dev/sdj

Note: It should go without saying, but make sure that /dev/sdj is actually your SD card!

Connect your Pi up to a monitor/TV and plug a keyboard and mouse in so that we can complete the initial set-up. When the first launch screen appears (yum, ncurses) opt to to the following

Resize root to fill SD card
Set Hostname (I went with RaspPiRouter)
Enable OpenSSH
Change the GPU memory allocation to 16MB (the system's going to be headless, why waste RAM on the GPU?)

Once ready, connect up an ethernet cable and reboot the Pi. For the time being it should get an IP via DHCP, you can either check the allocated IP on the HomeHub, or run

ip a

On the pi itself.

Connect Remotely

Now we want to SSH in and do a bit of configuration, so assuming the Pi got the IP 192.168.1.25

ssh pi@192.168.1.25

Enter 'raspberry' as the password. Now that we're in, the first thing to do is change the default password (everyone knows that it's raspberry)

passwd

Install Some Packages

We're largely going to install packages as we need them, but let's begin with the first two that we know we'll need

sudo -s # Saves me typing sudo before every command in this tutorial
apt-get install hostapd isc-dhcp-server

Configure Networking

Now we want to do a bit of IP allocation, the HomeHub grabs itself 192.168.1.254 and .253 so we're going to use .252, .251 and .250. What we're looking to do is to get the WLAN access point working with DHCP, once that's done we'll bridge the interfaces and let our DHCP server rule the entire LAN

ifdown wlan0
nano /etc/network/interfaces

#Remove all entries relating to wlan0 except for allow hotplug
# Then add:
iface wlan0 inet static
 address 192.168.1.251
 netmask 255.255.255.0

Save and exit

For now, we'll manually apply the IP to the interface

ifconfig wlan0 192.168.1.251

Configure HostAPD

The next step in configuring our wireless access point is to actually tell it what we want it to do, bear in mind this config file is nothing short of tetchy, so pay close attention to the values you use (don't try and use hw_mode n for example). Change the values of ssid and wpa_passphrase to suit your needs

nano /etc/hostapd/hostapd.conf

interface=wlan0
ssid=MyHomeNetwork 
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

Next we want to configure the system defaults to point to our config file

nano /etc/default/hostapd

# Add the following
DAEMON_CONF="/etc/hostapd/hostapd.conf"

Finally, we can fire up the WLAN AP to check everything works

/usr/sbin/hostapd /etc/hostapd/hostapd.conf
#At this point you should be able to see the wireless network from your phone/laptop. If you try and connect you'll see something like the following in the terminal (expect your connection to fail though)

Configuration file: /etc/hostapd/hostapd.conf
Failed to update rate sets in kernel module
Using interface wlan0 with hwaddr 80:1f:02:8d:5f:51 and ssid 'MyHomeNetwork'
wlan0: STA 00:37:6d:be:c7:c3 IEEE 802.11: authenticated
wlan0: STA 00:37:6d:be:c7:c3 IEEE 802.11: associated (aid 1)
wlan0: AP-STA-CONNECTED 00:37:6d:be:c7:c3
wlan0: STA 00:37:6d:be:c7:c3 RADIUS: starting accounting session 52C2E54A-00000000
wlan0: STA 00:37:6d:be:c7:c3 WPA: pairwise key handshake completed (RSN)

Your connection will likely have failed, unless the client you were connecting with happened to have a static IP. Press Ctrl+C to bring the AP back down and we'll move onto the all important next step

Configuring DHCP

So, now we want to configure the DHCP server

nano /etc/dhcp/dhcp.conf

# Comment out the following 
option domain-name "example.org";
option domain-name-servers ns1.example.org, ns2.example.org;

# Leave authoritative commented, we're not ready to replace the HomeHub just yet!

At the bottom of the file, add the following

subnet 192.168.1.0 netmask 255.255.255.0 {
range 192.168.1.150 192.168.1.200;
option broadcast-address 192.1.0.255;
option routers 192.168.1.254;
default-lease-time 600; 

max-lease-time 7200;
option domain-name "home";
option domain-name-servers 8.8.8.8, 8.8.4.4;
}

Save and close.

Static IPs

You may wish to reserve a specific IP for a specific machine, if so, re-open the dhcp configuration and add something similar to the following (one per machine)

host xbmc-eedb {
  hardware ethernet b8:27:eb:0b:ee:da;
  fixed-address 192.168.1.74;
}

Save and close, and the system with that MAC address will always be issued .74 (once the dchp server has been restarted

Now we need to configure the DHCP server to listen on WLAN0

nano /etc/default/isc-dhcp-server
#Set Interfaces to wlan0

Save and close, then bring up the DHCP server daemon

service isc-dhcp-server start

Note: if it fails, make sure WLAN0 still has the ip we assigned it -

ifconfig wlan0 192.168.1.251

If we start the WLAN AP again, you should now be able to connect - though you still won't be able to do much once on the network

/usr/sbin/hostapd /etc/hostapd/hostapd.conf

Your client should now receive an IP from within the range we specified, though it won't currently be able to route traffic to the internet. For that, we want a bridge, so Ctrl+C to kill hostapd one last time;

Creating a Bridge

Our final step before making everything start at boot, is to bridge our interfaces (I prefer this to NATting, it's one LAN after all!

apt-get install bridge-utils

Now we need to edit our network interfaces again

nano /etc/network/interfaces

# My values are below

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual
  address 192.168.1.252
  netmask 255.255.255.0
  gateway 192.168.1.254

iface default inet dhcp
allow hotplug wlan0
auto wlan0 br0

iface br0 inet static
 address 192.168.1.250
 broadcast 192.168.1.255
 netmask 255.255.255.0
 network 192.168.1.0
 gateway 192.168.1.254
 bridge_ports eth0 wlan0

Save and close.

When you run the next command, you will lose your SSH session, keep a note of the IP you defined for br0 as it's this one we'll need to SSH back in on

ifup br0

SSH back in, and to play it safe, run

service hostapd start
service networking restart

Now your client should be able to connect to the wifi and access the internet. If so, let's configure it all to start at boot

update-rc.d hostapd enable && update-rc.d isc-dhcp-server enable

wpa_supplicant might just undo all our hard work though, so lets disable it

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

It's at this point, we want to reboot the Pi just to be sure that everything will be as we left it if there is a power outage.

reboot

I initially found that DHCP requests would go unanswered following a reboot, it seems to be an issue with hostAPD and restarting the networking service after it's loaded resolves it. So (and this really isn't the correct way to fix an issue), I edited the init script for the DHCP server to include