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Wifi configuration • 3 Aug 2010

There's a difference how wireless is configured in FreeBSD 7 and 8. I found the following description on the FreeBSD forums:

8.0 also includes the VAP (virtual access point) stuff, which splits all wireless drivers into two parts: the hardware interface and the virtual interface(s).

Whereas in FreeBSD <= 7 you manipulate the wireless interface directly (ath0, wi0, wpi0, etc), in FreeBSD 8+ you first clone the interface and then manipulate the cloned interface.

You'll have something like an ath0 (the hardware interface) that you clone into a wlan0 (or whatever you want to call it). Then you configure the wlan0 interface.

The relevant chapter from the FreeBSD handbook is also a good read.

wifi card

FreeBSD 7

This example shows how to configure an Atheros card for connecting to a wireless router in WPA security mode. The card gets it IP address from the router via DHCP. Edit in /etc/rc.conf:

ifconfig_ath0="DHCP WPA" defaultrouter="192.168.1.1"

and in /etc/wpa_supplicant.conf:

network={ ssid="LinksysRouter" psk="Secret" }

The 'psk' above stands for 'pre-shared key'. If you use an hexadecimal psk, you should not quote it. (thanks Bubulein on FreeNode ##freebsd)

And here are relevant lines from my /usr/local/etc/kismet.conf:

source=radiotap_bsd_ab,ath0,ath0 defaultchannels=IEEE80211ab:1,6,11,2,7,12,3,8,13,4,9,14,5,10

FreeBSD 8

As said before, FreeBSD 8 requires you to first create a virtual interface, and then configure that interface. The example below uses a fixed IP. Edit in /etc/rc.conf:

wlans_ath0="wlan0" ifconfig_wlan0="WPA 192.168.1.48/27" defaultrouter="192.168.1.1"

and because the nameservers aren't provided by DHCP, this is in /etc/resolv.conf:

search mydomain.com nameserver 192.168.1.33 nameserver 192.168.1.1 nameserver 194.109.6.67

192.168.1.33 is a DNS server in my home network, 192.168.1.1 is the router (as a fallback), and 194.109.6.67 is the DNS server at my provider.

The /etc/wpa_supplicant.conf file is the same as the example I gave earlier.

Monitor mode

If you want to play with security tools like Kismet, you should also create a virtual interface that is allowed to go into monitor mode. That is done thus:

wlans_ath0="wlan0 wlan1" create_args_wlan1="wlanmode monitor" ifconfig_wlan0="WPA 192.168.1.48/27" defaultrouter="192.168.1.1"

...and then kismet is told to use wlan1 instead of wlan0. Edit in /usr/local/etc/kismet.conf:

source=radiotap_bsd_ab,wlan1,wlan1 defaultchannels=IEEE80211ab:1,7,13,2,8,3,14,9,4,10,5,11,6,12

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content last edited on October 31, 2010, 13:37 - rendered in 2.21 msec