ContentsBR TableOfContents(2)

attachment:IconsPage/IconControlCenter2.png attachment:IconsPage/IconFavourites.png attachment:IconsPage/IconHammer2.png attachment:IconsPage/IconDustTape.png attachment:IconsPage/IconArt-Small.png

This page was listed as needing a lot of love, which is very true. So just wanted to let you know, it's getting some love and under heavy construction. Ignore the mess and look at the content, lots of good stuff that may help you. And feel free to edit and help out as any Love you can offer is welcome here By the way: it would be a good idea to merge WifiDocs/WiFiTroubleshooting into this document

1. Purpose

This guide is meant to be a check list to troubleshoot wireless network connections. It will not solve all problems but hopefully guide you to find the problem area and help towards a resolution.
Before starting this guide have you tried to activate your card at all? Go into system>administration>networking. If you see your card in the list you may have a working driver and just need to set up the network properties and activate. If you do not get a working connection after this then come back and walk through the steps

2. Overview

2.1. Commands

Reading the commands section through is not necessary for this guide but it would be useful.
The first section will contain the commands associated with troubleshooting wireless. Detail about the command and some basics of what it does will be given. When going through the [#steps steps], anywhere a command is given it will link back to the command section.
With each command will be an example of the command with key points noted.
For more information on each command check the manual.
- man <command>
In each command I will use <>. This is to show where you need to input a value to complete the command. Do not include the <> symbols in your command.
- Where I use <ath0> in commands you need to replace this with your device's logical name (could be ath0; wlan0; eth1; etc...)
- <> Any where else you see this follow what's inside or instructions of what it says to put in the command.

2.2. Steps

The basic structure
- [#check Check for Device Recognition]
- [#driver Check for driver]
- [#connection Check for router connection]
- [#ip Check for ip address assignment]
- [#dns Connected but no internet]

This structure is setup in a specific order. You can not move on until you get everything resolved in the current step you're in. For example, step 3 is router association. You can not move on to the next step of ip assignment until you get router association. If you can't get past a step then you know where the problem area is. You can now look for more help in that specific area. Once it's resolved then move onto the next step.

2.3. Config files

Any config file used in wireless will be listed with notes about the particular file

2.4. Connected but no internet

This section will be devoted to those who have a working wireless connection but other problems occur such as dropped signal. This is a fragmented work in progress currently.

Anchor(commands)

3. Commands

This section gives a real brief summary of commands used to help you troubleshoot. There are also examples of the commands discussed. For more information, consult the man page of the command or do a google search.

Anchor(lshw)

3.1. lshw

This command shows information about hardware:
```
  sudo lshw
```

We can limit the the output to show just specific devices by adding options to the command:

```
  sudo lshw -businfo
```

attachment:IconsPage/IconExample48.png

BusInfo	Device	Class	Description
pci@00:1f.5		multimedia	82801CA/CAM AC'97 Audio Controller
pci@00:1f.6		communication	82801CA/CAM AC'97 Modem Controller
pci@03:00.0	ath0	network	AR5212 802.11abg NIC

{!} You can then use a different option to limit output so it shows just your networking devices.

Find your device in the list and notice it's class then:
```
  sudo lshw -C <class>
```

attachment:IconsPage/IconExample48.png

*-network
       description: Wireless interface
       product: AR5212 802.11abg NIC
       vendor: Atheros Communications, Inc.
       physical id: 1
       bus info: pci@03:00.0
       logical name: ath0
       version: 01
       serial: 00:11:95:50:be:62
       width: 32 bits
       clock: 33MHz
       capabilities: bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes '''driver=ath_pci driverversion=0.9.6.0 (EXPERIMENTAL)''' ip=192.168.1.12 multicast=yes wireless=IEEE 802.11g
       resources: iomemory:10800000-1080ffff irq:11

Key Points

Notice the configuration line. This area will tell you if there is a driver loaded for your device. (except devices using orinoco driver, these don't show here) If you do not see a driver listed here then there is not one loaded and assigned to the device and it will not show up in iwconfig output or the nework-admin gui.
The businfo line has importance as some devices are recognized and memory is readable but the device is not physically on the bus. This is rare but it has been seen. It may seem cryptic but your output will vary greatly and there needs to be some characters (other then 0) here denoting it's place in the pci bus.

Anchor(lspci)

3.2. lspci

This command lists information about devices on the pci bus:
```
  lspci -v
```
Lists out pci devices with information about the device. (information is different then output from lshw)

You can limit the output by piping the output with grep

```
  lspci -v | grep Ethernet
```

attachment:IconsPage/IconExample48.png

0000:03:00.0 Ethernet controller: Atheros Communications, Inc. AR5212 802.11abg NIC (rev 01)
        '''Subsystem: D-Link System Inc D-link DWL-G650 (Rev B5)''' Wireless cardbus adapter
        Flags: bus master, medium devsel, latency 168, IRQ 11
        Memory at 10800000 (32-bit, non-prefetchable) [size=64K]
        Capabilities: [44] Power Management version 2

  sudo lspci -n

0000:03:00.0 0200: '''168c:0013''' (rev 01)

Key Points

This command shows the revision of the card (in above example the revision of the card is B5 not 01).
Using the -n option you can find the PCI ID (168C:0013) of the card and find the correct driver to use with ndiswrapper. [http://ndiswrapper.sourceforge.net/mediawiki/index.php/list ndiswrapper list]

Anchor(lsusb)

3.3. lsusb

This command lists information about devices on the usb bus.
```
  sudo lsusb -v
```

attachment:IconsPage/IconExample48.png

$ lsusb
Bus 005 Device 001: ID 0000:0000
Bus 001 Device 001: ID 0000:0000
Bus 004 Device 002: ID 2001:3700 D-Link Corp. [hex] DWL-122 802.11b
Bus 004 Device 001: ID 0000:0000
Bus 003 Device 001: ID 0000:0000
Bus 002 Device 001: ID 0000:0000

Anchor(lsmod)

3.4. lsmod

This command simply shows what modules are loaded and running.
```
  sudo lsmod
```

When the command [#lshw lshw] was run, you saw the name of the driver allocated to the device. You can pipe this command through grep to limit the output.

```
  lsmod | grep ath
```

attachment:IconsPage/IconExample48.png

ath_pci                78908  0
ath_rate_sample        16776  1 ath_pci
wlan                  141532  4 wlan_wep,ath_pci,ath_rate_sample
ath_hal               148432  3 ath_pci,ath_rate_sample

Anchor(modprobe)

3.5. modprobe

modprobe runs or stops a module from running. Most wireless drivers in breezy are in a module form. The following commands remove or add a module.

When a recognized device loads, the kernel automatically loads the correct module for the device. This command is only needed to manually run a module

To start a module run this command:
```
  sudo modprobe <module>
```
To stop and remove a module run this command:
```
  sudo modprobe -r <module>
```

Anchor(iwconfig)

3.6. iwconfig

This command prints information about a wireless interface and allows you to configure the network interface from the command line.
```
  sudo iwconfig
```

attachment:IconsPage/IconExample48.png

* eth0      no wireless extensions.

* ath0      IEEE 802.11g  ESSID:"XXXXX"
          Mode- Managed  '''Frequency- 2.437 GHz'''  '''Access Point- 00:17:16:1D:FC:DE'''
          Bit Rate-36 Mb/s   Tx-Power-18 dBm   Sensitivity=0/3
          Retry- off   RTS thr:off   Fragment thr- off
          Encryption key:xxxx-xxxx-xx   Security mode:restricted
          Power Management off
          Link Quality=50/94  Signal level=-45 dBm  Noise level=-95 dBm
          Rx invalid nwid:10911  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

Key Points

This example shows the interface of ath0. If you do not see anything like this sample then you do not have a working driver.
Access Point: If you see all zeros here or nothing then you are not connected/associated to your router. When you are connected it will show the mac address of the router here.
Frequency more commonly known as channel. If you can not connect to your router ensure frequency is correct.

You can not set the channel(currently with breezy or earlier) via the network gui. Most drivers are set up as auto so it changes to the corresponding channel of the ap you're trying to connect to. But if you must make the change then this is the command to change it.

  sudo iwconfig <ath0> channel <X>
  or
  sudo iwconfig <ath0> freq <x.xxxG>

Channel/Frequency Chart
Ch 1	2.412
Ch 2	2.417
Ch 3	2.422
Ch 4	2.427
Ch 5	2.432
Ch 6	2.437
Ch 7	2.442
Ch 8	2.447
Ch 9	2.452
Ch 10	2.457
Ch 11	2.462
Ch 12	2.467
Non US Channels
Ch 13	2.472
Ch 14	2.484

Anchor(ifconfig)

3.7. ifconfig

This command is similar to iwconfig with the following differences.
- It's a more general networking command. It works with any interface whether wireless or wired.
- It's configuration options and output show different networking references or set different settings.
```
  sudo ifconfig
```

attachment:IconsPage/IconExample48.png

  ath0      Link encap:Ethernet  HWaddr 00:11:95:50:BE:62
          inet addr:192.168.1.11 Bcast:192.168.255.255  Mask:255.255.255.0
          inet6 addr: fe80::211:95ff:fe50:be62/64 Scope;Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:32568 errors:162786 dropped:0 overruns:0 frame:162786
          TX packets:17252 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:200
          RX bytes:20362191 (19.4 MiB)  TX bytes:6778264 (6.4 MiB)
          Interrupt:11 Memory:d0c80000-d0c90000

Key Points

The benefit with ifconfig on a wireless device is it shows if you have an ip address assigned to the device which is noted next to inet addr. iwconfig may show you're connected to your router but you still have no internet connection with out an ip address assigned to the device.

Anchor(iwlist)

3.8. iwlist

This command will give you more detailed information from the wireless interface such as a scan of all available routers with in range.
```
  sudo iwlist <ath0> scan
```

attachment:IconsPage/IconExample48.png

ath0      Scan completed :
          Cell 01 - Address: 00:13:46:1D:BC;0E
                    ESSID:"xxx"
                    Mode: Master
                    Frequency: 2.437 GHz (Channel 6)
                    Quality=49/94  Signal level=-46 dBm  Noise level=-95 dBm
                    Encryption key:on
                    Bit Rate:1 Mb/s
                    Bit Rate:2 Mb/s
                    Bit Rate:5 Mb/s
                    Bit Rate:6 Mb/s
                    Bit Rate:9 Mb/s
                    Bit Rate;11 Mb/s
                    Bit Rate;12 Mb/s
                    Bit Rate;18 Mb/s
                    Bit Rate;24 Mb/s
                    Bit Rate;36 Mb/s
                    Bit Rate;48 Mb/s
                    Bit Rate;54 Mb/s
                    Extra bcn_int=100

Key Points

If you get a completed scan like example, then your device and driver is probably working properly.
Some devices do not support scanning so this command may not work for you.(such as orinoco cards)

Anchor(dhclient)

3.9. dhclient

dhclient is simply the program that deals with dhcp if you're dealing with a router running as a dhcp server.
```
  sudo dhclient <ath0>
```

If you are associated with your router try running this command to get ip and other information to set up connection.

Anchor(ping)

3.10. ping

ping is a good troubleshooting command to track down where the connection problem may be: First ping your local loopback device
```
  ping -c 4 127.0.0.1
```

If this doesn't work then there is a problem in the tcp/ip stack some where.

If the device is assigned an ip address next ping that. use [#ifconfig ifconfig] to find the ip address assigned to the device
```
  ping -c 4 <192.168.1.11>
```
Next ping your router
```
  ping -c 4 <192.168.0.1>
```
Next ping an external site using the ip address
```
  ping -c 4 216.239.57.99
```
Next ping using common name
```
  ping -c 4 www.google.com
```

If you can ping an external site with the ip address but not the common name then there is a [#dns dns] nameserver problem

Anchor(steps)

4. Troubleshooting Steps

Anchor(check)

4.1. Check Device

Relevant@commands~$ [#lshw lshw] [#lspci lspci] [#lsusb lsusb]

4.1.1. PnP

Most devices are plug and play but it is worth checking.

plug and Play is a term used in the computer field to describe a computer's ability to have new device, normally peripherals, added without having to reconfigure or restart the computer. It is not a term stating the device will work as described immediately. A driver has to be installed so the os can communicate with the device

To check if device is recognized use the [#lshw lshw] command. If device shows up then you can check off step I

4.1.2. Non recognized card

Some devices are a little more difficult as they are not recognized when inserted into the os and little information about these will be here. More added later.
1. If card doesn't show up immediately try these steps but no guarantee this will solve problem.

Run the following command. Hopefully you'll get some output about the device.
```
  sudo pccardctl ident
```

attachment:IconsPage/IconExample48.png

  Socket 0:
    product info: "Atheros Communications, Inc.", "AR5001-0000-0000", "Wireless LAN Reference Card", "00"
    manfid: 0x0271, 0x0012
    function: 6 (network)

If you get no output then the memory on the card can not be read which could be the problem. Now we need to open a file and add this to the end of the file.

  gksudo gedit /etc/pcmcia/config.opts

the information you add should look like this.

attachment:IconsPage/IconExample48.png

card ""Atheros Communications, Inc.", "AR5001-0000-0000", "Wireless LAN"
  manfid 0x0271, 0x0012
  function: 6 (network)
  bind "ath_pci"

After making this change run this command

  sudo kill -HUP `cat /var/run/cardmgr.pid`

Now run [#lshw lshw] to see if card is recognized and loaded properly.

Most cards needing this will be older devices. You should not have to do this with any cards made in the past few years but there will be exceptions.

Notice I added the bind line which states what driver should be allocated to the device. You will need to find what driver your device uses. More on that in the next step.

4.1.2.1. problem with bridge in pci bus line

On several, especially new systems the Yenta bridge is not on the root PCI bridge, but behind a PCI-to-PCI bridge. On some x86 or x86_64 systems, these bridges aren't corrreclty set up by the BIOS, which may cause CardBus and even PCMCIA devices not to show up in lspci or in pccardctl ident correctly. If you suspect that this may be the cause, issue this command:
```
  lspci -v | grep subordinate
```
- Its result may be like this:
```
        Bus: primary=00, secondary=02, subordinate=04, sec-latency=64
        Bus: primary=02, secondary=03, subordinate=06, sec-latency=176
        Bus: primary=02, secondary=07, subordinate=0a, sec-latency=176
```
- Let's decode the first line: bus 0 (primary) is bridged to busses 2 (secondary) to 4 (subordinate) by a bridge. The second and the third line state that bus 2 is bridged to busses 3-6, and 7-10. However, the CPU (which itself is connected to bus 0 through the root bridge) needs to be able to access all these busses. If you try to walk the tree to bus 7, for example, you see that the CPU can't get there, as bus 0 is only bridged to busses 2 to 4.
If this is the case, or you find a message stating "try pci=assign-busses" in the dmesg log, append the following to the kernel boot line:
```
        pci=assign-busses
```

4.1.3. System locks upon card insertion

What usually happens here is a problem reading the card memory which is the first thing that happens when card is inserted. You can try this to see if it helps. Open the file /etc/pcmcia/config.opts (you need root privledges to modify this file). You will see a section like this.

attachment:IconsPage/IconExample48.png

  include memory 0xc0000-0xfffff
  include memory 0xa0000000-0xa0ffffff
  include memory 0x60000000-0x60ffffff

Change this so it looks like this

  include memory 0xd0000-0xdffff
  include memory 0xc0000-0xcffff
  include memory 0xc8000-0xcffff
  include memory 0xd8000-0xdffff

Anchor(driver)

4.2. Device Drivers

Relevant@commands~$ [#lshw lshw] [#lsmod lsmod] [#modprobe modprobe]

Your device may be supported in Ubuntu with a native driver. Before anything else you should check to see if a driver automatically loaded. Use the [#lshw lshw] command for this.

4.2.1. General device information

[http://doc.gwos.org/index.php/Networkwifi UDSF networkwifi section]
[http://linux-wless.passys.nl/ Linux wireless devices.]

attachment:IconsPage/IconNote.png Devices using the ralink chipset are listed with the rt2x00 driver. the rt2x00 driver only works for kernels 2.6.13 or greater. For a kernel older then this you need to use rt2500 for pci devices or rt2570 for usb devices

4.2.2. Native Linux Drivers

You can find general driver information, driver notes specific to ubuntu releases, and links to more help on the drivers [http://doc.gwos.org/index.php/Networkwifi here].

Anchor(ndisc)

4.2.3. ndiswrapper for non supported cards

Not all cards/devices have a linux driver. If you find your card is not supported you will have to look at an app called ndiswrapper.

[http://ndiswrapper.sourceforge.net/mediawiki/index.php/List You can check here to see if your card is supported by ndiswrapper.]
[wiki:WifiDocs/Driver/Ndiswrapper full information on ndiswrapper kept on this page] including troubleshooting help specific to ndiswrapper.

Sometimes ndiswrapper is used prematurely. There may be a native driver that comes with Ubuntu which is taking the primary driver position and conflicting with ndiswrapper. In such cases, if the native driver does not work properly with your card you want to use ndiswrapper, you can blacklist the native driver, by adding a file to /etc/modprobe.d/ . The file name must begin with the blacklist prefix. In this file you can blacklist modules (so that they will not be loaded upon card chipset recognition) with the following syntax :

```
  blacklist modulename
```

For example, if you own a D-Link DWL-G520+ card which uses the ACX111 chipset, and you plan to use the ndiswrapper module, you have to blacklist the acx module, by creating the file /etc/modprobe.d/blacklist-acx with a single line inside which states :

```
  blacklist acx
```

4.2.4. Check driver

If you ran [#lshw lshw] and saw a driver bound to the device then let's test to make sure it's communicating to the kernel.
1. run the command [#lsmod lsmod] to see if driver is loaded. (look for the name that was listed under lshw). If you did not see it in the list then use the [#modprobe modprobe] command to load it.
2. run the command [#iwconfig iwconfig]. If you see out put like in the example in the command section then the driver is at least identifying the device as a wireless device to the kernel.
  1. Opening networking in system>administration> and seeing the device in the list is how to identify through gui if driver is at least communicating to the kernel at a basic level.
3. run the command [#iwlist iwlist] to scan for a router. If an access point is identified this is a second identifier which shows the driver as communicating and shows that it's probably working as it can complete a wireless interface task. (note not all cards support scanning so this may not work for you)

4.2.5. Driver looks ok, device disabled

Newer laptops come with features to disable the wireless radio to save battery when not in use. Usually this is switched by a FN+Fx key combo or specific button for the purpose. It is possible driver and everything is ok but the wireless device is in the disabled state and can't be used. Using the designated key(s) in linux sometimes does not work.
Usually this is apparent by running the [#lshw lshw] command you see *-network:1 DISABLED or if you run the [#iwconfig iwconfig] command you see eth1 NOT READY!. So how do you rectify this? It varies so much the exact solution can't be put here in this document for all the different models. So...
Look at the LaptopTestingTeam page here on the wiki to see if your laptop is listed with any information.
Do a google search using terms such as manufacture, model, linux, wireless, enable, button, radio....etc. When searching and finding similar pages that don't help, use words that are used in those pages to help you search.
Go to the [http://ubuntuforums.org ubuntu forums] and ask, maybe someone else has the same laptop and knows the work around.

Anchor(connection)

4.3. Router Connection

Relevant@commands~$ [#iwconfig iwconfig]

With the driver loaded go to the panel System>Administration>Networking. Highlight your device and click properties. Enter your networking info, click ok then try to activate.
1. You should see an applet in the panel showing a connection. (You may need to set properties to show correct interface)
2. You can check if you're associated to router by running the command [#iwconfig iwconfig].
You can also connect to the router via the command line using the command [#iwconfig iwconfig]. The syntax looks like this.

  sudo iwconfig <ath0> essid <essid> ap <xx:xx:xx:xx:xx:> key <XXX> mode <> commit

note: not all these may be used, check the man page for more informatin

If you can not connect to the router then try these.
1. Change to an open signal (instead of wep or wpa). This may be an unattractive option but it's a short term one to make sure the card and ap can connect. Once you've verified this then you can add encryption back in.
  1. When using wep more people seem to have success using an open key instead of shared and a hexadecimal method instead of ascii. But there should be no reason any setting shouldn't work. Try the settings you want and consider adjusting if you have problems.
  2. To get wpa working you will need to install the wpasupplicant from the repositories. There are instructions for various drivers on using wpa. See notes on wpa below.
2. Download a scanner such as [:NetworkManager:network manager], [http://ubuntuforums.org/forumdisplay.php?f=74/ gtk wifi], or [http://www.bitbuilder.com/wifi_radar/ wifi radar]. of course this is not an option if you can not connect to the internet without wireless
3. Try booting with kernel option pci=noacpi or acpi=off as acpi sometimes conflicts with network devices. The second option will affect power management.
4. Check for firmware update on the router and update it if there is newer firmware available.

4.3.1. Notes on wep

[https://www.ubuntulinux.org/support/documentation/faq/helpcenterfaq.2004-10-07.0031507315/ ubuntu wep faq]
If you have a 10 digit wep key try entering it in this format xxxx-xxxx-xx (include dashes)
Use an open setting instead of shared when using wep
When using wep, check driver files such as README as some drivers need a command to adjust the mode to work properly. Here are a couple examples.
- Madwifi driver needs to change to authmode 2 when using shared key setting.
  - manually from command line iwpriv ath0 authmode 2
  - add line pre-up iwpriv ath0 authmode 2 to interfaces file to automate during boot
- For ipw2200 driver interface file should say wireless-key restricted <key>

4.3.2. Notes on wpa

[http://hostap.epitest.fi/ Information on host AP; hostapd; wpa_supplicant]
[https://wiki.ubuntu.com/WifiDocs/Driver/Ndiswrapper ndiswrapper w/ wpa]
[https://wiki.ubuntu.com/WPAHowto WPA HowTo]
[http://doc.gwos.org/index.php/Ipw2200_wpa ipw2200 and WPA]
[http://www.madwifi.org/wiki/UserDocs/802.11i madwifi/atheros and wpa]

There have been a few posts where no association is established with router even on an open signal. At the point of writing this line, no answer has been seen to why this happens. A router reboot has been noted once to resolve but in other situations has caused heartache as network settings need to be set up again. Booting with acpi=off or noapci should be tried.

Anchor(ip)

4.4. ip assignment

Now that you have association to the router did you get an ip assigned to the device? This can be checked two ways.
1. Run the command [#ifconfig ifconfig] and look for an assigned ip.
2. You can always try to [#ping ping] the router with the routers ip. A lot of home routers use something similar to 192.168.0.1 You'll have to find what that ip address is to ping.
If you do not have an ip then here are things to try
- Using DHCP
```
  sudo dhclient <ath0>
```
or
```
  sudo invoke-rc.d networking restart
```

after running the invoke-rc.d command try dhclient ath0 again

attachment:IconsPage/IconNote.png You may want to try and reboot making sure your networking [#config interfaces] file is set up properly.

Using Static ip assignment
- ```
  sudo ifconfig <ath0> down
```
```
  sudo ifconfig ip addr 192.168.x.x netmask 255.255.255.0 broadcast 192.168.x.255 up
```
  where the x = an ip address in your network range.
```
  sudo route add default gw <router_ip> dev <ath0>
```
- Now try to [#ping ping] your router and a website. If you're connected now and have an ip assigned but can not surf website then move on to next section.
- You will need to make sure your [#config interfaces] file is set up properly so you get internet again when you reboot

Anchor(dns)

4.5. Connected but no internet

4.5.1. DNS

If you don't know what DNS means or what it does you can go [http://en.wikipedia.org/wiki/DNS/ here] to read more. Basically it takes a common name such as www.google.com and searches a database to find the ip address of google. Then it actually transfers the request to download the web page via the ip address. If you are connected to your router and have an ip address assigned to your wireless device but can't search the web, you will need to check to see if you have a DNS nameserver set
- A simple test to see if it's a DNS server setting is to use the [#ping ping] command. If you can ping an external site via ip address but can't load a web page in your browser then it is possible you have a dns server problem.
- Check this file to see if there is a dns server listed.
```
  cat /etc/resolv.conf
```

attachment:IconsPage/IconExample48.png

```
  search telus.net
  nameserver 209.53.4.130
  nameserver 209.53.4.150
```
- You can find your dns settings if you have a working windows machine
  - For a Win 95/98 box click start>run then type winipcfg. Choose the correct adapter and then more. In the sample above, replace telus.net with what's in the "Host Name" box. name server will equal what's in the dns server box.
  - For a Win 2000/xp box click Start>Run...type cmd click ok. type ipconfig /all. In the sample above, replace telus.net with what's next to the field Connection-Specific DNS suffix. For name server look next to the line DNS servers.
- Your DNS server settings can also be found out by calling your isp provider and asking them.
You can set up your dns settings so they don't change.BR
- StaticDnsWithDhcp:StaticDnsWithDhcp

Anchor(ipv6)

4.5.2. IPV6

The internet standard is currently considered ipv4. ipv6 is a new standard that is slowly being implemented to replace ipv4. Because it's not widely used right now, ipv6 can cause problems. ipv6 is turned on by default in Ubuntu. This can cause no internet if above seems ok.
- Firefox specific
  - In the address bar type about:config. Find this line network.dns.disableIPv6 and double click on it to change the value to true.
- System wide
  Open the file /etc/modprobe.d/aliasesBR Add the first three lines to the file. The line with # starting is already in the file. Find it and add the # in front of it.
alias net-pf-10 ipv6 offBR alias net-pf-10 offBR alias ipv6 offBR #alias net-pf-10 ipv6
After making these changes a reboot is required.

Anchor(config)

5. Config Files

The following is a list of important config files used with wireless
- /etc/network/interfacesBRThis is where your inteface settings for the network are kept [http://www.linuxplanet.com/linuxplanet/tutorials/5736/3/ sample]
  1. man interfaces has information about this file.
  2. For a little more detailed info on the interfaces file look at the file in /usr/share/doc/ifupdown/examples/network-interfaces.gz. You can read through it with the cat command and then adding | less to the end of the command.
  3. For pcmcia users who want to start your card at boot do not use an auto stanza. add map <ath0> to the file. So here is an example of what it would look like.
Check your routers settings to ensure it can accept another connection.
Check your /etc/network/intefaces file. You should have something similar to this:

attachment:IconsPage/IconExample48.png

# The loopback network interface auto lo iface lo inet loopback # This is a list of hotpluggable network interfaces. # They will be activated automatically by the hotplug subsystem. # With lines # out these don't work. If they were removed this would hotplug only eth0 when cable is plugged in with active network #mapping hotplug # script grep # map eth0 #echo connects ath0 when device is hotplugged. using echo instead of grep allows any device to be brought up when hotplugged. Note this could cause a problem if a device is active and another one that is mapped is plugged in. mapping hotplug script echo map ath0 #interfce of ath0 device with wep setting (not all these lines are required but show you options that may be needed) iface <ath0> inet dhcp wireless-essid xxxx wireless-key xxxxx wireless-key xxxx-xxxx-xx (in certain situations a - is needed after every 4 characters to work) wireless-key1 xxxx (add a number after key to specify key number to use.) wireless-defaultkey 1 (specifies which key is default) wireless-key s:xxx (add s: in front of key if ascii form) wireless-key XXXXXXXXXX open|restricted (if using shared/restricted setting add this line) auto <ath0>

/etc/resolv.confBRWhere your DNS server settings are kept
/etc/modulesBRIf a driver won't load at boot, you can add it to this list so it does
/etc/modprobe.d/blacklistBRIf you don't want a driver to load at boot you add it to this list. Usually this is used if you have a driver conflict and you want to make sure a specific driver is used. Note: this method will not work unless it is a LKM (loadable kernel module) If driver/mod was compiled into the base kernel, it will still load if on blacklist.

Anchor(special)

6. Connected but problems

This section is reserved for solutions to problems where you can get connected but the connection is unstable. If you find a solution to your problem that's not here, please edit this page and add your solution.

6.1. Dropped Connections

One of the more common problems is channel interference. If you are having a problem with dropped connections then try to use a different channel.
Network-Manager; Wifi-radar; and gtk wifi can cause dropped signals as every so often it scans the interfaces. When doing this the connection drops. Try to uninstall these apps to see if your problem goes away. If it solves your problem, find out how you can help improve the apps perforance by contacting either ubuntu's developers or the apps developers.

6.2. Connected butproblems with certain sites

Disable [#ipv6 IPV6] to see if it helps.

6.3. Wrong driver loads at boot

Some devices you will find load multiple drivers for what ever reason. To prevent a driver from loading during boot read the [#modprobe modprobe] command section.
Anchor(links)

6.4. Links

These are sites with information on wireless networking:

[http://oob.freeshell.org/nzwireless/LWAP-HOWTO.html linux wireless access point HOWTO]BR [http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/ Wireless linux resources]BR [http://www.tldp.org/HOWTO/NET3-4-HOWTO.html/ tldp Linux networking howto]BR [http://www.us.debian.org/doc/manuals/reference/ch-gateway.en.html Debian Network Configuration]BR [http://users.linpro.no/janl/hardware/wifi.html Survey of Linux and Wifi]BR

CategoryDocumentation CategoryCleanup CategoryNetworking

Ubuntu Documentation

WifiDocs/WirelessTroubleShootingGuide

1. Purpose

2. Overview

2.1. Commands

2.2. Steps

2.3. Config files

2.4. Connected but no internet

3. Commands

3.1. lshw

3.2. lspci

3.3. lsusb

3.4. lsmod

3.5. modprobe

3.6. iwconfig

3.7. ifconfig

3.8. iwlist

3.9. dhclient

3.10. ping

4. Troubleshooting Steps

4.1. Check Device

4.1.1. PnP

4.1.2. Non recognized card

4.1.2.1. problem with bridge in pci bus line

4.1.3. System locks upon card insertion

4.2. Device Drivers

4.2.1. General device information

4.2.2. Native Linux Drivers

4.2.3. ndiswrapper for non supported cards

4.2.4. Check driver

4.2.5. Driver looks ok, device disabled

4.3. Router Connection

4.3.1. Notes on wep

4.3.2. Notes on wpa

4.4. ip assignment

4.5. Connected but no internet

4.5.1. DNS

4.5.2. IPV6

5. Config Files

6. Connected but problems

6.1. Dropped Connections

6.2. Connected butproblems with certain sites

6.3. Wrong driver loads at boot

6.4. Links