How To: Troubleshoot your Wireless Network Connection - Connecting at Command Line

[kevdog]

In setting up their wireless connection for the first time, Im discovering many individuals having problems connecting through Network Manager or other GUI wireless connection tools. In fact my Network Manager is intermittently buggy, connecting sometimes and not others. This guide benefits all users in case the GUI tools are not working, and is useful for testing a wireless connection during initial installation of wireless drivers since it provides for good debugging output.

Unencrypted/ WEP / WPA connections will be covered in this guide.
This guide is for anyone attempting to establish a network connection manually at the command line.

Pre-requisites
1. Properly installed network driver -- This guide can be used to troubleshoot driver installation to see if it is properly functioning
2. The ESSID of your router must be broadcasted and not hidden
3. Knowlege of your wireless cards driver (please see Prerequisite #4 to determine driver). Those using the r8187/r818x driver please see the end of the guide
4. Knowledge of your wireless card's Interface Name - The user must know the proper interface of the wireless connection (wlan0, eth1, rausb1, etc). To discover this information, at command line type:

lshw -C network

There may be multiple interfaces listed, however look under the section appropriate to your wireless device for the line labeled logical name. Here is an example:

  *-network               
       description: Wireless interface
       product: BCM4306 802.11b/g Wireless LAN Controller
       vendor: Broadcom Corporation
       physical id: 0
       bus info: pci@06:00.0
       logical name: wlan0
       version: 03
       serial: 00:12:17:35:17:10
       width: 32 bits
       clock: 33MHz
       capabilities: bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=ndiswrapper+lsbcmnds driverversion=1.48rc1+Cisco-Linksys ,LLC.,02/1 ip=192.168.1.101 latency=64 multicast=yes wireless=IEEE 802.11g
       resources: iomemory:3c000000-3c001fff irq:11

In the example above the interface name is wlan0. I will refer to the interface name throughout the rest of this guide as <interface>.

For people first setting up their connection, please note that the above also lists the driver used for the network card. In the example above, the driver used is ndiswrapper. If your network device comes back UNCLAIMED or there is no driver listed, then you have not correctly installed the driver for your device. You must review the procedures for installation of your wireless driver.

__________________________________________________ __________________________
Unencrypted Connection

All commands typed at the command line:

sudo ifconfig <interface> down
sudo dhclient -r <interface>
sudo ifconfig <interface> up
sudo iwconfig <interface> essid "ESSID_IN_QUOTES"
sudo iwconfig <interface> mode Managed
sudo dhclient <interface>

__________________________________________________ __________________________
WEP Connection

You must have either your 64bit or 128 bit HEX Key or the ASCII Equivalent of your HEX Key.

sudo ifconfig <interface> down
sudo dhclient -r <interface>
sudo ifconfig <interface> up
sudo iwconfig <interface> essid "ESSID_IN_QUOTES"
sudo iwconfig <interface> key HEX_KEY <<<-------- If using ASCII Equivalent, this is s:ASCII_KEY (please make note of the prefix s:)
sudo iwconfig <interface> mode Managed
sudo dhclient <interface>

__________________________________________________ __________________________
WPA Connection - WPA-PSK or WPA2-PSK

Requirements: In most cases the wpa_supplicant package is required in order to connect via WPA. If you have a working ethernet or unencrypted/WEP wireless connection, this package may be installed via:

sudo aptitude install wpasupplicant

If only wireless is available, I would recommend that an unencrypted connection first by established and tested first before directly proceeding to make a WPA connection. WPA adds another layer of complexity.

1. Creation of /etc/wpa_supplicant.conf file

At command line:

gksu gedit /etc/wpa_supplicant.conf

Inside the file add the following for WPA(1):

ap_scan=1
ctrl_interface=/var/run/wpa_supplicant 

network={
        ssid="ESSID_IN_QUOTES"
        scan_ssid=0
        proto=WPA
        key_mgmt=WPA-PSK
        psk="ASCII PSK Password in Quotes"
        pairwise=TKIP
        group=TKIP
}

For WPA(2):

ap_scan=1
ctrl_interface=/var/run/wpa_supplicant 

network={
        ssid="ESSID_IN_QUOTES"
        scan_ssid=0
        proto=WPA
        key_mgmt=RSN
        psk="ASCII PSK Password in Quotes"
        pairwise=TKIP CCMP
        group=TKIP CCMP
}

***Word of caution -- In some cases I have found WPA(2) to have different settings than the above. Some Broadcom cards use the pairwise/group TKIP cipher for WPA2 rather than CCMP. I would suggest all initially use WPA(1) and then later convert to WPA2 since some variations to the above may be needed

2. Connect via command line

sudo ifconfig <interface> down
sudo dhclient -r <interface>
sudo wpa_supplicant -w -D<****see footer below***> -i<interface> -c/etc/wpa_supplicant.conf -dd 
sudo ifconfig <interface> up
sudo iwconfig <interface> mode Managed
sudo dhclient <interface>

***footer
The value listed here is dependent on the driver you have installed. Typing man wpa_supplicant at command line will give you the full gamut of choices however a quick reference
ndiswrapper=wext (use wext and not ndiswrapper despite what documentation might suggest)
ath_pci = madwifi
ipw2100/2200=ipw

__________________________________________________ __________________________
A successful connection in all cases will results in this:

user@computer:~$ sudo dhclient wlan0
There is already a pid file /var/run/dhclient.pid with pid 134993416
Internet Systems Consortium DHCP Client V3.0.4
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

Listening on LPF/wlan0/00:12:17:35:17:10
Sending on   LPF/wlan0/00:12:17:35:17:10
Sending on   Socket/fallback
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 4
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 7
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 7
DHCPOFFER from 192.168.1.1
DHCPREQUEST on wlan0 to 255.255.255.255 port 67
DHCPACK from 192.168.1.1
bound to 192.168.1.101 -- renewal in 299133 seconds.

The computer in this example has received an IP address of 192.168.1.101

__________________________________________________ __________________________
Users of RTL 8180, RTL8185, RTL 8187 using the built in native r8187 / r818x drivers

By default the r8187 and r818x drivers are blacklisted due to a know bug. These drivers are usuable however with a twist to the above methods

If you want to try using these drivers, please load the kernel modules:

sudo modprobe r818x
sudo modprobe r8187

These drivers require a bogus or extra letter be suffixed to the essid name in order for these drivers to work
For example if your are trying to connect to a router with essid=Router, at he command line you would type essid=Routerx. Notice the extra x or bogus character. I have provided an example using the unencrypted connection procedure below, however this extra character needs to be used if attempting to connect to all network types (unencrypted/ WEP / WPA)

sudo ifconfig <interface> down
sudo dhclient -r <interface>
sudo ifconfig <interface> up
sudo iwconfig <interface> essid "Routerx"
sudo iwconfig <interface> mode Managed
sudo dhclient <interface>

If these drivers work for you, and you would like these drivers to load automatically at startup for you, avoiding to have to type sudo modprobe everytime, please edit your blacklist file:

gksu gedit /etc/modprobe.d/blacklist

And comment out (or prefix the following lines with a # sign). You want the following lines to appear as below:

#blacklist r8187
#blacklist r818x

__________________________________________________ __________________________
Useful Commands

ifconfig - lists IP address (similar to ipconfig in Windows)
iwlist scan - shows wireless networks that are available in the area along with basic encryption information
lshw -C network - Shows interface and driver associated with each networking device
lspci -nn - Shows hardware connected to the pci bus
lsusb - Shows USB connected hardware
lshw -C usb - Additional info on USB related hardware (good for USB dongles)
cat /etc/modprobe.d/blacklist - List modules that will not be loaded by the Operating System at boot time
lsmod - lists currently loaded kernel modules. (Example usage - lsmod | grep ndiswrapper)
route -n - Lists kernel IP routing table -- Good for troubleshooting problems with the gateway
cat /etc/resolve.conf - Lists DNS servers associated with network connections
sudo modprobe ***** - Loads the kernel module **** . (Example usage - sudo modprobe ndiswrapper, sudo modprobe r818x, sudo modprobe ath_pci)
sudo modprobe -r **** - Unloades the kernel module ****. (Example usage - sudo modprobe -r ndiswrapper)
sudo ifup/ifdown <interface> - Brings up/down the interface and clears the routing table for the specified interface
sudo ifconfig <interface> up/down - Brings up/down the interface for the specified interface
sudo dhclient <interface> - Request IP address from DNS server for specified interface
sudo dhclient -r <interface> - Release IP address associated with specified interface
sudo iptables -L - Lists firewall rules
dmesg | more - Lists boot log -- good for troubleshooting problems with modules/drivers not being loaded
uname -r - Displays kernel version

Further references:
Ra chipsets - rt2500, rt73, rt61, rt2570 drivers - http://ubuntuforums.org/showthread.p...=serial+monkey - Author diepruis
Ndiswrapper installation for Broadcom chipsets - http://ubuntuforums.org/showthread.php?t=475963 - Author Jamie Jackson
Madwifi website for certain Atheros Chipsets - http://madwifi.org/ -- If your Atheros chipset is listed on this website - it should work out of the box with installation of the linux restricted drivers package for your kernel version

[GSF1200S]

Hey thanks alot for this.. this will help me immensely. I dont even run a network manager, so this is especially useful as a result of you listing the CLI to use. Until now Ive been afraid to use WPA 1-2, but I think it will be a good learning experience.

Thanks again...

[Lucho77]

Thanks kevdog for your post, I can connect with no problem.
Only one thing, after issue 'lshw -C network' in the line:
logical name: wifi0
That labeled logical name did not work for me, so I changed for ath0 and follow the next step for WEP connection and it did the trick.
Thanks again.

[kevdog]

Thanks for pointing that out -- I know the madwifi driver makes a physical interface name for the device -wifi0, and then creates a default virtual interface ath0. Its possible to make more virtual interfaces if you needed them. Ive found this out with my own Atheros card. I dont know of a way to convey this to people specifically b/c wifi0 is mentioned in the lshw -C network statement, and ifconfig/iwlist scan show both the ath0 and wifi0 interfaces (which are actually the same device). Maybe somebody could help me with this one!

[cudds]

thanks for the help - connection is much more stable - how would I script this up to run at boot for all users? When I run wpa_supplicant it doesn't finish running so I have to bring another terminal up for the rest

[chrisN_uk]

Thanks for the guide. I'm coming across a problem though,

sudo wpa_supplicant -w -Dwext -iwlan0 -c/etc/wpa_supplicant.conf
Line 7: invalid key_mgmt 'RSN'
Line 7: no key_mgmt values configured.
Line 7: failed to parse key_mgmt 'RSN'.
Line 11: failed to parse network block.
Failed to read or parse configuration '/etc/wpa_supplicant.conf'.

Any idea what's wrong? I think I don't have something installed...

[mrpresident]

hmmm im trying this.
got up to

pa_supplicant -w -D bcm43xx -i eth2 -c/etc/wpa_supplicant.conf -dd

but then it tells me that the dirver is unsupported.
can anyone help a n00b?

i think i am using the bcm43xx driver version 2.6.22-14-generic.
iremember installing the restricted driver thing when i installed ubuntu on this comp.

[kevdog]

Directly from the man wpa_supplicant pages:

Available Drivers The available drivers to specify with the -D option are: hostap (default) Host AP driver (Intersil Prism2/2.5/3). (this can also be used with Linuxant DriverLoader). hermes Agere Systems Inc. driver (Hermes-I/Hermes-II). madwifi MADWIFI 802.11 support (Atheros, etc.). atmel ATMEL AT76C5XXx (USB, PCMCIA). wext Linux wireless extensions (generic). ndiswrapper Linux ndiswrapper. broadcom Broadcom wl.o driver. ipw Intel ipw2100/2200 driver. wired wpa_supplicant wired Ethernet driver bsd BSD 802.11 support (Atheros, etc.). ndis Windows NDIS driver.

I think you want to use either broadcom or wext for your driver rather than specifying bcm43xx

[rabiddachshund]

I just upgraded from Feisty to Gutsy. I have a linksys wmp54g (using the ralink that worked in Feisty. Gutsy sees the network with ~80% signal but it just won't connect to it. My network is unsecure and broadcasted. I followed your steps but no dice. Here's my terminal; maybe there's something I'm missing:

david@TheBeast:~$ lshw -C network WARNING: you should run this program as super-user. *-network description: Ethernet interface product: 82573L Gigabit Ethernet Controller vendor: Intel Corporation physical id: 0 bus info: pci@0000:04:00.0 logical name: eth0 version: 01 serial: 00:12:3f:79:66:e8 width: 32 bits clock: 33MHz capabilities: bus_master cap_list ethernet physical configuration: broadcast=yes driver=e1000 driverversion=7.3.20-k2-NAPI firmware=0.4-1 latency=0 module=e1000 multicast=yes *-network description: Wireless interface product: RT2561/RT61 802.11g PCI vendor: RaLink physical id: 5 bus info: pci@0000:05:05.0 logical name: wmaster0 version: 00 serial: 00:1a:70:a6:34:6d width: 32 bits clock: 33MHz capabilities: bus_master cap_list logical ethernet physical wireless configuration: broadcast=yes driver=rt61pci latency=64 module=rt61pci multicast=yes wireless=IEEE 802.11g david@TheBeast:~$ sudo ifconfig wmaster0 down david@TheBeast:~$ sudo dhclient -r wmaster0 Internet Systems Consortium DHCP Client V3.0.5 Copyright 2004-2006 Internet Systems Consortium. All rights reserved. For info, please visit http://www.isc.org/sw/dhcp/ wmaster0: unknown hardware address type 801 wmaster0: unknown hardware address type 801 Listening on LPF/wmaster0/ Sending on LPF/wmaster0/ Sending on Socket/fallback david@TheBeast:~$ sudo ifconfig wmaster0 up SIOCSIFFLAGS: Operation not supported david@TheBeast:~$ sudo iwconfig wmaster0 essid "default" Error for wireless request "Set ESSID" (8B1A) : SET failed on device wmaster0 ; Operation not supported. david@TheBeast:~$ sudo iwconfig wmaster0 mode Managed Error for wireless request "Set Mode" (8B06) : SET failed on device wmaster0 ; Operation not supported. david@TheBeast:~$ sudo dhclient wmaster0 There is already a pid file /var/run/dhclient.pid with pid 134519120 Internet Systems Consortium DHCP Client V3.0.5 Copyright 2004-2006 Internet Systems Consortium. All rights reserved. For info, please visit http://www.isc.org/sw/dhcp/ wmaster0: unknown hardware address type 801 wmaster0: unknown hardware address type 801 Listening on LPF/wmaster0/ Sending on LPF/wmaster0/ Sending on Socket/fallback DHCPDISCOVER on wmaster0 to 255.255.255.255 port 67 interval 4 DHCPDISCOVER on wmaster0 to 255.255.255.255 port 67 interval 9 DHCPDISCOVER on wmaster0 to 255.255.255.255 port 67 interval 14 receive_packet failed on wmaster0: Network is down DHCPDISCOVER on wmaster0 to 255.255.255.255 port 67 interval 4 send_packet: Network is down No DHCPOFFERS received. No working leases in persistent database - sleeping. david@TheBeast:~$

For some reason Network Manager lists the card as ra0 so I tried it with that:

david@TheBeast:~$ sudo ifconfig ra0 down [sudo] password for david: david@TheBeast:~$ sudo dhclient -r ra0 There is already a pid file /var/run/dhclient.pid with pid 6220 killed old client process, removed PID file Internet Systems Consortium DHCP Client V3.0.5 Copyright 2004-2006 Internet Systems Consortium. All rights reserved. For info, please visit http://www.isc.org/sw/dhcp/ wmaster0: unknown hardware address type 801 wmaster0: unknown hardware address type 801 Listening on LPF/ra0/00:1a:70:a6:34:6d Sending on LPF/ra0/00:1a:70:a6:34:6d Sending on Socket/fallback david@TheBeast:~$ sudo ifconfig ra0 up david@TheBeast:~$ sudo iwconfig ra0 essid "default" david@TheBeast:~$ sudo iwconfig ra0 mode Managed david@TheBeast:~$ sudo dhclient ra0 There is already a pid file /var/run/dhclient.pid with pid 134519120 Internet Systems Consortium DHCP Client V3.0.5 Copyright 2004-2006 Internet Systems Consortium. All rights reserved. For info, please visit http://www.isc.org/sw/dhcp/ wmaster0: unknown hardware address type 801 wmaster0: unknown hardware address type 801 Listening on LPF/ra0/00:1a:70:a6:34:6d Sending on LPF/ra0/00:1a:70:a6:34:6d Sending on Socket/fallback DHCPDISCOVER on ra0 to 255.255.255.255 port 67 interval 6 DHCPDISCOVER on ra0 to 255.255.255.255 port 67 interval 9 DHCPDISCOVER on ra0 to 255.255.255.255 port 67 interval 16 No DHCPOFFERS received. No working leases in persistent database - sleeping. david@TheBeast:~$

I tried to format it as closely as possible, but it's not quite right because I'm having to use windows to post this

HOLY CRAP! I figured I'd try to connect through network manager one last time before posting this and it worked!
What just happened?

[Flare183]

Most of the time if you modprobe your wireless card, then type in sudo dhclient will work.