Turn Raspberry PI3 into WI-FI router with HOSTAPD

Following this tutorial you’ll be able to configure your RaspBerryPi model 3 to accept incoming connections using its built-it WiFi antenna and to forward the requests to the Ethernet port.

Requirements

• 1x RaspBerryPi model 3 (earlier versions will not work unless you have a WiFi dongle. In that case, just follow this Adafruit tutorial)
• 1x Ethernet cable
• Ethernet access

Context

My current ISP provided me with an old, locked WiFi router that is only capable to broadcast 20mb/s, which is not great for my nominal 100mb/s connection. Furthermore, it messes up my home devices assigning them to different subnets (and sometimes, it mixes local devices with ipv4 and ipv6). Using a Chromecast or a simple Plex server is therefore becoming a bit of an hassle and I thought for a moment that I needed a new WiFi router. Then I realised that most WiFi routers are basically tiny Linux computers with firmware sugar on top of them: so why not turning my RPI into a more useful WiFi router? Please note that this project is basically a proof of concept: the on-board WiFi antenna hasn’t a great range and the top-speed goes barely over 30mb/s. However, seen that this method works, I’ll try to run it with a powerful WiFi USB dongle with AP support to see if the PI can be converted to a more serious 300mb/s router.

Also, this tutorial is a slight modification from this Adafruit tutorial that is meant for RaspBerryPi < v3 and requires a WiFi dongle.

Let’s get on with it, shall we?

Initial checks

Once logged in to your Pi (via Terminal, on another computer), check that everything is setup:

Generally, eth0 is the ethernet connection and wlan0 the WiFi connection. If both are there, we’re good to go.

Software setup

We’ll install and configure 2 programs:

• hostapd
• isc-dhcp-server

DHCP server

Now, with this configuration we are assigning the subnet192.168.42.10–50(40 devices in total) and we are configuring our WiFi local IP address to be 192.168.42.1. While we’re at it, we’re assigning Google’s public DNS: 8.8.8.8, 8.8.4.4.

Next, let’s specify on what interface should the DHCP server servce DHCP requests (wlan0 in this case):

Let’s setup wlan0 for static IP:

Hostapd

Some tutorials requires you to set a driver ID. If you need to do that, in order to check what is your current driver ID, run:

…but even though my driver ID reads brcmfmac_sdio, if I put it into the hostapd.conf file I still got an error, but commenting out does the trick.

Next, let’s configure the network address translation:

Let’s test our access point by running:

You should now be able to see your pi WiFi, connect to it and access internet to it. As a quick comparison, streaming 4k videos will consume about 10% of the pi CPU so… use it accordingly.

As a bonus, if you want to check what’s happening on your WiFi hotspot, check the log file:

If you really feel naughty, (or if you want to prevent naughty behaviour from your connected devices…) let me know in the comments below if you’re interested in a tutorial on how to configure a honeypot with your pi.