Di Linux desktop yang sudah memiliki Network Manager, mengatur koneksi wireless tidak terlalu sulit. GUI untuk wireless sudah cukup mudah untuk dipakai. Tapi bagaimana bila saya tidak punya tampilan GUI hanya console terminal saja? Saya belum pernah sebelumnya mengatur koneksi wireless tanpa bantuan Network Manager. Tadi saya belajar cara mengatur koneksi WiFi di Ubuntu 12.04 lewat command line. Tentu saja saya harus mematikan Network Manager (menu GUI) terlebih dulu.
root@x220:~# /etc/init.d/network-manager stop
Bila access point yang dipakai menggunakan autentikasi (WPA,WPA2) maka untuk mengatur koneksi wireless-nya kita perlu aplikasi wpa_supplicant. Install dulu dengan perintah berikut :
root@x220:~# apt-get install wpasupplicant
root@x220:~# dpkg -l | grep wpasupplicant
ii wpasupplicant 0.7.3-6ubuntu2 client support for WPA and WPA2 (IEEE 802.11i)
root@x220:~#
Di laptop saya wireless adapter-nya dikenali sebagai wlan0, maka saya perlu mendaftarkannya dulu ke dalam file /etc/network/interfaces :
root@x220:~# cat /etc/network/interfaces
auto lo
iface lo inet loopback
auto wlan0
iface wlan0 inet dhcp
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
root@x220:~#
Untuk masalah autentikasi password, saya perlu mengatur file wpa_supplicant.conf seperti berikut ini :
root@x220:~# cat /etc/wpa_supplicant/wpa_supplicant.conf
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=root
network={
ssid="GBT733"
scan_ssid=1
proto=WPA RSN
key_mgmt=WPA-PSK
pairwise=CCMP TKIP
group=CCMP TKIP
psk=da5d79195468cf3f7cb498731beac2136e8b9fccd11d90182a8d668ddbd660bb
}
root@x220:~#
Beberapa detil yang perlu dipahami dari konfigurasi di atas adalah :
ssid : nama access point.proto : tipe wireless security yang dipakai oleh access point. Bisa WPA (Wi-Fi Protected Access) atau RSN (Robust Security Network). RSN ini juga dikenal sebagai WPA2 (Wi-Fi Protected Access II).key_mgmt : menentukan tipe enkripsi dari wireless password-nya. WPA-PSK (WPA Pre-shared Key). Kenapa WPA-PSK karena access point saya menggunakan mode sekuriti WPA2-Personal.pairwise & group : mengatur tipe algoritma enkripsi dari password Wi-Fi.psk : pre shared key hasil enkripsi dari ASCII password
PSK didapat dari hasil enkripsi password Wi-Fi yang berupa text (password Wi-Fi yang kita kenal sehari-hari). Misalnya access point saya menggunakan nama SSID GBT733 dan password-nya adalah ‘testingpassword‘, untuk mendapat WPA PSK saya gunakan perintah berikut ini :
root@x220:~# wpa_passphrase GBT733 testingpassword
network={
ssid="GBT733"
#psk="testingpassword"
psk=da5d79195468cf3f7cb498731beac2136e8b9fccd11d90182a8d668ddbd660bb
}
root@x220:~#
Setelah semua sudah diset, tinggal restart network service-nya dengan perintah :
root@x220:~# /etc/init.d/networking restart
* Running /etc/init.d/networking restart is deprecated because it may not enable again some interfaces
* Reconfiguring network interfaces... ssh stop/waiting
ssh start/running, process 13925
[ OK ]
root@x220:~#
Di syslog saya bisa lihat DHCP client mencoba mengakses access point & meminta IP address :
root@x220:~# tail -f /var/log/messages
Feb 26 10:53:27 x220 kernel: [273753.765617] iwlwifi 0000:03:00.0: L1 Enabled; Disabling L0S
Feb 26 10:53:27 x220 kernel: [273753.765806] iwlwifi 0000:03:00.0: Radio type=0x1-0x2-0x0
Feb 26 10:53:27 x220 kernel: [273753.894034] ADDRCONF(NETDEV_UP): wlan0: link is not ready
Feb 26 10:53:27 x220 dhclient: DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 3
Feb 26 10:53:30 x220 dhclient: DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 4
Feb 26 10:53:31 x220 wpa_supplicant[13818]: Trying to authenticate with 90:f6:52:43:82:44 (SSID='GBT733' freq=2437 MHz)
Feb 26 10:53:31 x220 wpa_supplicant[13818]: Trying to associate with 90:f6:52:43:82:44 (SSID='GBT733' freq=2437 MHz)
Feb 26 10:53:31 x220 kernel: [273757.284480] wlan0: authenticate with 90:f6:52:43:82:44 (try 1)
Feb 26 10:53:31 x220 kernel: [273757.287179] wlan0: authenticated
Feb 26 10:53:31 x220 kernel: [273757.287454] wlan0: associate with 90:f6:52:43:82:44 (try 1)
Feb 26 10:53:31 x220 kernel: [273757.291546] wlan0: RX AssocResp from 90:f6:52:43:82:44 (capab=0x431 status=0 aid=2)
Feb 26 10:53:31 x220 kernel: [273757.291550] wlan0: associated
Feb 26 10:53:31 x220 wpa_supplicant[13818]: Associated with 90:f6:52:43:82:44
Feb 26 10:53:31 x220 kernel: [273757.299586] ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
Feb 26 10:53:31 x220 wpa_supplicant[13818]: WPA: Key negotiation completed with 90:f6:52:43:82:44 [PTK=CCMP GTK=TKIP]
Feb 26 10:53:31 x220 wpa_supplicant[13818]: CTRL-EVENT-CONNECTED - Connection to 90:f6:52:43:82:44 completed (auth) [id=0 id_str=]
Feb 26 10:53:31 x220 kernel: [273757.358903] wlan0: Wrong control channel in association response: configured center-freq: 2437 hti-cfreq: 2417 hti->control_chan: 2 band: 0. Disabling HT.
Feb 26 10:53:34 x220 dhclient: DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 9
Feb 26 10:53:34 x220 dhclient: DHCPREQUEST of 192.168.1.112 on wlan0 to 255.255.255.255 port 67
Feb 26 10:53:34 x220 dhclient: DHCPOFFER of 192.168.1.112 from 192.168.1.1
Feb 26 10:53:34 x220 dhclient: DHCPACK of 192.168.1.112 from 192.168.1.1
Feb 26 10:53:34 x220 dhclient: bound to 192.168.1.112 -- renewal in 36185 seconds.
Terlihat proses autentikasi sukses & wireless adapter saya mendapat IP 192.168.1.112.
root@x220:~# ifconfig wlan0
wlan0 Link encap:Ethernet HWaddr 10:0b:a9:a1:f5:b8
inet addr:192.168.1.112 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::120b:a9ff:fea1:f5b8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:556117 errors:0 dropped:0 overruns:0 frame:0
TX packets:1859518 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:96155942 (96.1 MB) TX bytes:2764438662 (2.7 GB)
root@x220:~#
