How do I troubleshoot problems with my wireless connection?

Question

Let's say I have a problem with my wireless connection. What commands should I run to share their output with a tech-savvy friend or an online support community?

For example:

• How can I tell if my wireless card is recognised?
• How can I get information on which wireless networks are within range?
• How can I tell if I am connected to a wireless, but not the Internet?

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I'm asking this question because I'm seeing many questions about problems with wireless connections, without many details, like this one. It would be useful if I could point to this question so that the asker can improve their question with more information. I'm hoping for a comprehensive answer with all the details, or with links to other generic questions for brevity.

Answer 1

To check if the card is recognized, run:

sudo lshw -C network

or

lspci -nnk | grep -iA2 net

The second command is useful, as it shows the vendor and product IDs [8086:4222]:

~$ lspci -nnk | grep -iA2 net
06:00.0 Network controller [0280]: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection [8086:4222] (rev 02)
    Subsystem: Hewlett-Packard Company PRO/Wireless 3945ABG [Golan] Network Connection [103c:135c]
    Kernel driver in use: iwl3945
    Kernel modules: iwl3945

Example - card recognized, brand and model are correctly identified, correct driver is in use (driver=iwl3945), and wireless connection is established (ip=192.168.2.81):

sudo lshw -C network
[sudo] password for hp: 
  *-network               
       description: Wireless interface
       product: PRO/Wireless 3945ABG [Golan] Network Connection
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:06:00.0
       logical name: wlan0
       version: 02
       serial: 00:13:02:c8:d2:75
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=iwl3945 driverversion=3.2.0-35-generic firmware=15.32.2.9 ip=192.168.2.81 latency=0 link=yes multicast=yes wireless=IEEE 802.11abg
       resources: irq:45 memory:80000000-80000fff

To see the networks within range, just click the network icon in the panel. If you prefer a command, run nm-tool.

To make sure you are connected to a wireless, but not an ethernet network, first identify the wireless interface (usually wlan0, eth1 or eth2) by looking at the output of sudo lshw -C network. Then, look for an IP address to tell which interface is connected.