View Full Version : [ubuntu] Connected to wifi, but cannot access internet

September 5th, 2010, 09:03 PM
right, so I've been using my upstairs computer with no problems recently up until this evening, when I rebooted it did an automatic scan of my disks, so I left it to it's thing and when I came back ubuntu had successfully booted, and had seemingly successfully connected to my wireless network as usual.

I've been through the wireless troubleshooting guide, paying special attention to sections 4 and 6 but to no avail, while I'm apparently connected, and have been assigned an IP by my router I'm unable to access anything outside my computer, including the router itself.

This happened before, however I solved it by reinstalling ubuntu, and I'd rather not do that again! There's a beer in it for the person who can help me fix it :)

output of ifconfig

eth0 Link encap:Ethernet HWaddr 00:1c:25:38:8e:de
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

lo Link encap:Local Loopback
inet addr: Mask:
inet6 addr: ::1/128 Scope:Host
RX packets:9475 errors:0 dropped:0 overruns:0 frame:0
TX packets:9475 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1103438 (1.1 MB) TX bytes:1103438 (1.1 MB)

wlan0 Link encap:Ethernet HWaddr 00:1f:1f:31:d0:28
inet addr: Bcast: Mask:
inet6 addr: fe80::21f:1fff:fe31:d028/64 Scope:Link
RX packets:1059 errors:0 dropped:0 overruns:0 frame:0
TX packets:349 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:344345 (344.3 KB) TX bytes:27044 (27.0 KB)

output of route

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface * U 2 0 0 wlan0
link-local * U 1000 0 0 wlan0
default UG 0 0 0 wlan0

output of cat /etc/networking/interfaces

auto lo
iface lo inet loopback

September 5th, 2010, 09:25 PM
oh, and just to confirm that it's a problem with that computer, here's the readout from my router

LAN > DHCP Client List

This page shows you the IP address, Host Name and MAC address of each computer that is connected to your network. If the computer does not have a host name specified, then the Host Name field will be blank. Pressing "Refresh" will update the list.

IP Address Host Name MAC Address main-desktop 00:19:21:E8:4D:08 android_39ca93e7e30 00:23:76:08:00:33 paul-desktop 00:1F:1F:31:D0:28 <<< this is the one cause me problems

September 5th, 2010, 09:26 PM
I've got exactly the same problem on my computer. I'm clueless as to what's causing it. . Ironically, when I first tried to post this I couldn't do it. I had to disconnect and then reconnect.

(a very frustrated) andy

September 5th, 2010, 11:02 PM

September 6th, 2010, 01:23 AM
In addition to WiFi and IP connectivity you need to have Domain Name Service (DNS) configured. When you enter the textual URL for a web location, your computer sends a DNS-query to a specific DNS server. This server returns the numeric IP address that corresponds to the URL that you entered. Then your computer re-initiates it's connection request using this IP address that it got from the DNS server.

Before trying to set up DNS, we need to determine if this is really your problem. You can do this by accessing something out on the Internet using it's numeric IP address instead of entering it's textual URL in your browser. For instance, the numeric IP address for google is so you can go to your browser and enter "". This should get you to a Google page. If this works then your problem may be lack of a DNS server or local DNS services. If it does not work, then you have some other problem that may not be DNS related.

There are several excellent tutorials available on-line to help you configure your DNS functions and to assign a DNS server. One readily available open DNS server would be that provided by Google. Their DNS server IP addresses are at and
I have found their DNS service to be fast and reliable.

You can also go to a terminal page and enter "ping -c3" to see if your computer is actually passing commands to the Internet and receiving them back from Internet based entities.

September 6th, 2010, 09:01 AM
Thanks for the reply, as I said though, I've been through thr wireless networking troubleshooter including the checking of my dns settings. Just to make my problem clear though, the computer boots without error, connects to my network fine and according to syslog is able to connect to and negotiate with my router and receive its IP. The router shows it on the DHCP client list and network manager shows the relevant and correct details. However I cannot connect to any external server using either normal www.server.com dns addresses or IP. I can ping localhost but not the ip address of my router, nor any other server.

That's about as thorough as I can be right now.

September 6th, 2010, 11:58 AM