Raspberry Pi Wifi Static IP

My RPi is going to be a telepresence robot so it uses wifi. It also needs a static IP address. Here's how to configure Raspbian Wheezy with a static IP for wifi. Included are two useful techniques. Follow the series of steps and options below.

You can configure Wheezy for 1. Roaming with Static IP, below, or 2. Static IP With No Roaming, WPA2, PSK, below.

1. Roaming With Static IP

By default, Wheezy is configured for wireless roaming using wpa_supplicant, a daemon that manages roaming and authentication to access points with WPA, WPA2, WEP, or no encryption. With it, you can specify multiple access points and your RPi will join them automatically. First you'll need to add a Static IP Configuration, below.

a. Static IP Configuration

First, edit your /etc/network/interfaces and add the following to specify a static IP for demo which is any arbitrary name that we can use in the wpa_supplicant.conf to associate any network with this static IP configuration. You'll also make sure you have your wlan interface configured correctly.

allow-hotplug wlan0 iface wlan0 inet manual wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf

iface demo inet static

address 192.168.0.4
netmask 255.255.255.0
gateway 192.168.0.1

Next, you'll configure wpa_supplicant. Add a specification for a network Without Encryption below, With Encryption, WPA2, PSK below, or Any Network Specification below.

b. Without Encryption

To specify a network without encryption, edit  /etc/wpa_supplicant/wpa_supplicant.conf, add your network specification to the end of the file as follows. Specifying key_mgmt=NONE says the AP does not require encryption. To use the static IP configuration that you added in your interfaces, set id_str="demo" or whatever name you chose.

network={
 ssid="BotThoughts"
 scan_ssid=0
 key_mgmt=NONE
 priority=5
 id_str="demo"
}

Now proceed to the 3. Final Steps below.

2b. With Encryption, WPA2, PSK

To specify a network with WPA2 encryption using PSK (pre-shared key), edit /etc/wpa_supplicant/wpa_supplicant.conf, add a network specification to the end of the file as follows. To use the static IP configuration that you added in your interfaces, set id_str="demo" or whatever name you chose.

network={
 ssid="your-ssid-here"
 scan_ssid=0
 psk="your-pre-shared-key-here"
 proto=RSN
 key_mgmt=WPA-PSK
 pairwise=CCMP
 auth_alg=OPEN
 priority=1
 id_str="demo"
}




Now proceed to 3. Final Steps below.

2c. Any Network Specification

The bottom line is that you can add any network specification, following various online examples, to wpa_supplicant.conf and use a static IP for that access point simply by adding  id_str="demo" or whatever name you chose in interfaces.

In fact, you can have multiple strings, like home, work, traveling, demo, etc. Once you have edited wpa_supplicant.conf and interafaces, proceed to the 3. Final Steps below.

2. Static IP With No Roaming, WPA2, PSK 

This config does not use wpa_supplicant and is for WPA2 personal with PSK (Private Shared Key). The changes to your /etc/network/interfaces file will result in something like the following.

auto lo

iface lo inet loopback
iface eth0 inet static
address 192.168.0.5
netmask 255.255.255.0
gateway 192.168.0.1

auto wlan0
allow-hotplug wlan0
iface wlan0 inet static
address 192.168.0.4
netmask 255.255.255.0
gateway 192.168.0.1
wpa-passphrase yourpassphrasehere
wpa-ssid yourssidhere
wireless-channel yourchannelhere

#wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
#iface default inet dhcp

Specify using static instead of manual for interface wlan0, then specify the address, netmask, and gateway, configure the WPA passphrase and SSID, and the wireless channel. Finally, you have to disable the wpa_supplicant configuration, and you have to disable the default dhcp behavior.

Proceed to 3. Final Steps below.

3. Final Steps

After making your configuration file changes, either reboot, or issue the following commands to restart the wlan0 interface:

sudo ifdown wlan0
sudo ifup wlan0

If you get no errors on the last command, except possibly some ioctl errors, you're a-ok.

pi@raspberrypi:/etc/network$ sudo ifup wlan0
ioctl[SIOCSIWAP]: Operation not permitted
ioctl[SIOCSIWENCODEEXT]: Invalid argument
ioctl[SIOCSIWENCODEEXT]: Invalid argument
pi@raspberrypi:/etc/network$

Double-check by issuing iwconfig to make sure the RPi is joined to the access point, then use ifconfig wlan0, make sure it's configured correctly, then issue a ping to your gateway (ping 192.168.0.1) and then ping google.com or some other reliable website.

pi@raspberrypi:/etc/network$ ifconfig -a
eth0      Link encap:Ethernet  HWaddr b8:27:eb:fb:8d:50
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:36 errors:0 dropped:0 overruns:0 frame:0
          TX packets:36 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:3480 (3.3 KiB)  TX bytes:3480 (3.3 KiB)

wlan0     Link encap:Ethernet  HWaddr 80:1f:02:86:ef:61
          inet addr:192.168.0.4  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:38 errors:0 dropped:1467 overruns:0 frame:0
          TX packets:14 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:841044 (821.3 KiB)  TX bytes:100717 (98.3 KiB)

pi@raspberrypi:/etc/network$ ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_req=1 ttl=64 time=3.07 ms
64 bytes from 192.168.0.1: icmp_req=2 ttl=64 time=1.90 ms
^C
--- 192.168.0.1 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 1.905/2.491/3.077/0.586 ms
^C

Et voila, you have a wifi static IP. Congratulations!

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