Jens segers on Jan 26 2012

OSX: scan Wi-Fi networks with AirPort command line tool

I recently bought a new router and was going through the basic configuration. Like most routers, the default Wi-Fi channel is set to automatic. This means that when your router boots, it will scan nearby Wi-Fi networks and choose the best channel available. Usually this is your best option, but in my situation my router did not detect other networks and selected a random channel.

But in my room - which is closer to the street - I do detect other networks that may cause interference with my wireless signal. In the search of a wireless network scanner utility, I found out that strangely hidden for the average user, lies a command line airport utility that allows you to view, configure, and troubleshoot your Mac’s wireless connection. This utility is located at:

/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport

Typing the above command path can be avoided by creating a symbolic link to the command in /user/sbin/ by copying and pasting the command below into a terminal window.

sudo ln -s /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport /usr/sbin/airport

This will prompt you for a root password, enter it and hit return. Now you will be able to simply type airport in the terminal window to execute the command.

A few options are available:

macbook:~ Jens$ airport --help
Supported arguments:
 -c[<arg>] --channel=[<arg>]    Set arbitrary channel on the card
 -z        --disassociate       Disassociate from any network
 -I        --getinfo            Print current wireless status, e.g. signal info, BSSID, port type etc.
 -s[<arg>] --scan=[<arg>]       Perform a wireless broadcast scan.
                                  Will perform a directed scan if the optional <arg> is provided
 -x        --xml                Print info as XML
 -P        --psk                Create PSK from specified pass phrase and SSID.
                                  The following additional arguments must be specified with this command:
                                  --password=<arg>  Specify a WPA password
                                  --ssid=<arg>      Specify SSID when creating a PSK
 -h        --help               Show this help

But the most interesting option for me was airport --scan, which scans all available wireless networks and shows detailed information about them, including their channel:

macbook:~ Jens$ airport --scan
     SSID BSSID             RSSI CHANNEL HT CC SECURITY (auth/unicast/group)
   Segers 58:6d:8f:a0:5f:00 -86  36,+1   Y  -- WPA(PSK/AES,TKIP/TKIP) WPA2(PSK/AES,TKIP/TKIP)
    WiFi1 00:18:02:82:b3:00 -84  6       N  BE WEP
    WiFi2 00:1c:df:ed:a9:00 -76  6,-1    Y  US WEP
    WiFi3 06:18:02:82:b3:00 -87  6       N  BE NONE
    WiFi4 5c:35:3b:01:a3:00 -84  1       Y  BE NONE
    WiFi5 5c:35:3b:01:a3:00 -83  1       Y  BE WPA(PSK/TKIP,AES/TKIP) WPA2(PSK/TKIP,AES/TKIP)
   Segers 58:6d:8f:a0:5f:00 -81  11      Y  -- WPA(PSK/AES,TKIP/TKIP) WPA2(PSK/AES,TKIP/TKIP)

With this information you should be able to find out which channel is still available for your network. In my case channel 11 was a good choice since 1 and 6 were used by other networks. Keep in mind that channels close to each other will still overlap and interfere:

wifi channels


Comments

drdawning 5 months ago

Rad. Excellent. Thank you.


lukas 2 years ago

VGHS :)


Olivier 3 years ago

Good to know!