Fedora Linux

The up argument is also unnecessary if an IP address is being specified.

The previous command can therefore be written much more simply:

# ifconfig wlan0 192.168.9.37
# ifconfig wlan0
wlan0 Link encap:Ethernet HWaddr 00:0C:2D:00:2B:DB
       inet addr:192.168.9.37 Bcast:192.168.9.255 Mask:255.255.255.0
       inet6 addr: fe80::20c:2dff:fe00:2bdb/64 Scope:Link
       UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
       RX packets:1 errors:0 dropped:0 overruns:0 frame:0
       TX packets:18 errors:0 dropped:0 overruns:0 carrier:0
       collisions:0 txqueuelen:1000
       RX bytes:268 (268.0 b) TX bytes:2922 (2.8 KiB)

3.2.1.3.1. Configuring wireless networks from the command line

For wireless interfaces, there are two additional commands that are useful for configuration: iwconfig , which sets wireless parameterssuch as the channel, encryption, and ESSIDand iwlist , which can be used to scan for available networks.

iwconfig will display current settings if no parameters are given:

# iwconfig
lo no wireless extensions.
eth0 no wireless extensions.
sit0 no wireless extensions.
wlan0 IEEE 802.11b ESSID:'' Nickname:'zd1201'
         Mode:Managed Channel:6 Access Point: 00:90:4C:7E:00:29
         Bit Rate:11 Mb/s
         Retry:off RTS thr:off Fragment thr:off
         Encryption key:off
         Power Management:off
         Link Quality:0/128 Signal level=60/128 Noise level:0/128
         Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
         Tx excessive retries:0 Invalid misc:0 Missed beacon:0

Here you can see that this interface has associated with an access point with a MAC address of 00:90:4C:7E:00:29, and which is apparently an 802.11b network (11 Mb/s).

To scan for available networks, use iwlist with the scan argument:

# iwlist scan
lo Interface doesn't support scanning.
eth0 Interface doesn't support scanning.
sit0 Interface doesn't support scanning.
wlan0 Scan completed :
        Cell 01 - Address: 00:90:4C:7E:00:29
                     ESSID:'fedorabook'
                     Mode:Master
                     Channel:11
                     Bit Rates:1 Mb/s
                     Bit Rates:2 Mb/s
                     Bit Rates:5.5 Mb/s
                     Bit Rates:11 Mb/s
                     Encryption key:off
                     Quality=60/128 Signal level=-76 dBm Noise level=-100 dBm
         Cell 02 - Address: 00:87:29:13:c0:71
                     ESSID:'tylers'
                     Mode:Master
                     Channel:2
                     Bit Rates:1 Mb/s
                     Bit Rates:2 Mb/s
                     Bit Rates:5.5 Mb/s
                     Bit Rates:11 Mb/s
                     Bit Rates:18 Mb/s
                     Bit Rates:24 Mb/s
                     Bit Rates:36 Mb/s
                     Bit Rates:54 Mb/s
                     Encryption key:on
                     Quality=59/128 Signal level=-76 dBm Noise level=-99 dBm

To select which network wlan0 associates with, set the extended service set identifier (ESSID) of the interface:

# iwconfig wlan0 essid fedorabook
# iwconfig wlan0
wlan0 IEEE 802.11b ESSID:'fedorabook' Nickname:'zd1201'
         Mode:Managed Channel:6 Access Point: 00:90:4C:7E:00:29
         Bit Rate:11 Mb/s
         Retry:off RTS thr:off Fragment thr:off
         Encryption key:off
         Power Management:off
         Link Quality:0/128 Signal level=76/128 Noise level:0/128
         Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
         Tx excessive retries:0 Invalid misc:0 Missed beacon:0

To disable an interface, turn it down using ifconfig :

# ifconfig wlan0 down
# ifconfig wlan0
wlan0 Link encap:Ethernet HWaddr 00:0C:2D:00:2B:DB
         inet addr:192.168.9.37 Bcast:192.168.9.37 Mask:255.255.255.0
         BROADCAST MULTICAST MTU:1500 Metric:1