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Thread: Ethernet connection not recognised.

  1. #1
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    Ethernet connection not recognised.

    I've just installed 12.04 LTS as a dual boot alongside Windows 7 on my desktop PC which is home networked, but upon start-up it keeps telling me that a network cable is unplugged and therefore I have no internet connection nor a connection to my home network. Yet when I boot W7 there is no problem.
    Could someone please suggest the likely cause(s) and how to rectify the problem, as I've exhausted my limited Ubuntu knowledge in attempting to find the solution?
    Many thanks in advance to responders.

  2. #2
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    Re: Ethernet connection not recognised.

    Thread moved to Networking & wireless.
    If you believe everything you read, you better not read. ~ Japanese Proverb

    If you don't read the newspaper, you're uninformed. If you read the newspaper, you're mis-informed. - Mark Twain

  3. #3
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    Re: Ethernet connection not recognised.

    Hi

    I'll get the ball rolling for you. We need more information on your hardware.

    Please post the output of

    Code:
    sudo lshw -c network
    Enter your password. It will not be echoed to the screen.

    Also post the output of

    Code:
    lspci -nn | grep -i net
    Kind regards
    If you believe everything you read, you better not read. ~ Japanese Proverb

    If you don't read the newspaper, you're uninformed. If you read the newspaper, you're mis-informed. - Mark Twain

  4. #4
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    Re: Ethernet connection not recognised.

    Thanks Matt. As I have no network access from my Ubuntu installation, I have uploaded both the outputs to one file in my DropBox from a screen photo, which can be accessed from:
    https://www.dropbox.com/sh/2ilhn0swsep2u4j/ZdbAnwA9KOI look forward to your comments.
    Thanks and regards,
    Roger

  5. #5
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    Ubuntu 12.04 Precise Pangolin

    Re: Ethernet connection not recognised.

    There might be a useful suggestion or two here:
    http://ubuntuforums.org/archive/inde...t-1978608.html

  6. #6
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    Re: Ethernet connection not recognised.

    Hi

    Quote Originally Posted by gordintoronto View Post
    There might be a useful suggestion or two here:
    http://ubuntuforums.org/archive/inde...t-1978608.html
    There are some good suggestions in the link above to try.

    You have a driver installed for the network card and it looks to be up and running correctly.

    I'll give you some other things to check as well.

    From the terminal

    Code:
    cat /sys/devices/pci0000:00/0000:02:01.0/net/eth0/carrier
    If it's physically connected to the router you would expect to see a value of 1. If it returns a vlue of 0 then you are not physically connected to the router. Check your cabling etc.

    I may have got the path incorrect. If so then check

    Code:
    cat /sys/devices/pci0000:00/*/net/eth0/carrier
    If the path is still incorrect then run this command to find it.

    Code:
    find /sys -name carrier
    On my server... Look for the path with eth0 in it.

    Code:
    server1:/home/matthew % find /sys -name carrier                                  
    /sys/devices/virtual/net/lo/carrier
    /sys/devices/pci0000:00/0000:00:04.0/net/eth0/carrier
    find: ‘/sys/kernel/debug’: Permission denied
    server1:/home/matthew %

    On my server...

    Code:
    server1:/home/matthew % cat /sys/devices/pci0000:00/*/net/eth0/carrier
    1
    server1:/home/matthew % cat /sys/devices/pci0000:00/0000:00:04.0/net/eth0/carrier
    1
    server1:/home/matthew %
    Check network-manager is running correctly

    Code:
    service network-manager status
    Expect to see output like this

    Code:
    matthew-S206:/home/matthew/Music % service network-manager status
    network-manager start/running, process 1063
    matthew-S206:/home/matthew/Music %
    Check you have an ip address.

    Code:
    ifconfig eth0
    Expect output such as

    Code:
    server1:/home/matthew % ifconfig eth0
    eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx:xx  
              inet addr:192.168.0.103  Bcast:192.168.0.255  Mask:255.255.255.0
              UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              RX packets:1132 errors:0 dropped:0 overruns:0 frame:0
              TX packets:486 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:1000 
              RX bytes:124491 (124.4 KB)  TX bytes:70162 (70.1 KB)
              Interrupt:22 
    
    server1:/home/matthew %
    See if you can ping things.

    Try to ping your local router

    Code:
    ping -c3 <ip_address_of_router>
    Then try an external site

    Code:
    server1:/home/matthew % ping -c3 8.8.8.8
    PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
    64 bytes from 8.8.8.8: icmp_req=1 ttl=46 time=33.8 ms
    64 bytes from 8.8.8.8: icmp_req=2 ttl=46 time=26.6 ms
    64 bytes from 8.8.8.8: icmp_req=3 ttl=46 time=29.3 ms
    
    --- 8.8.8.8 ping statistics ---
    3 packets transmitted, 3 received, 0% packet loss, time 2003ms
    rtt min/avg/max/mdev = 26.600/29.933/33.848/2.990 ms
    server1:/home/matthew %
    Perform a lookup on a name

    Code:
    nslookup www.google.com
    Expect to see output like this...
    Code:
    server1:/home/matthew % nslookup www.google.com
    Server:        192.168.0.1
    Address:    192.168.0.1#53
    
    Non-authoritative answer:
    Name:    www.google.com
    Address: 173.194.67.147
    Name:    www.google.com
    Address: 173.194.67.99
    Name:    www.google.com
    Address: 173.194.67.103
    Name:    www.google.com
    Address: 173.194.67.105
    Name:    www.google.com
    Address: 173.194.67.104
    Name:    www.google.com
    Address: 173.194.67.106
    
    server1:/home/matthew %
    Each of these steps will help to isolate the problem area.

    Post back if required on how far you got.

    Kind regards
    Last edited by matt_symes; May 4th, 2013 at 10:39 PM.
    If you believe everything you read, you better not read. ~ Japanese Proverb

    If you don't read the newspaper, you're uninformed. If you read the newspaper, you're mis-informed. - Mark Twain

  7. #7
    Join Date
    Jun 2008
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    Re: Ethernet connection not recognised.

    Thanks Matt (and also thanks to gordintoronto).
    Here is the link to the output of your suggested code: ifconfig eth0
    https://dl-web.dropbox.com/get/publi...O4RJ-wDLim83Fg
    There's no inet addr but only some code unrecognised by me.
    Note also its name as being inet6 addr and not just inet
    The router is not recognising it as being connected.
    The various code you suggested before this produced results as expected and it is connected to the router - which is a Netgear DG-834 v4 and works fine under W7.
    Your further thoughts would be greatly appreciated.
    I'm now going to work through the link gordintoronto suggested.
    Thanks again and regards,
    Roger

  8. #8
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    Re: [SOLVED] Ethernet connection not recognised.

    Thanks to gordintoronto (and to Matt). Job done!
    The first suggestion in the link posted by gordintoronto solved the issue.
    Internet now connected and networked printer also now installed.
    Grateful thanks to both of you.
    Bestest,
    Roger

  9. #9
    Join Date
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    Re: Ethernet connection not recognised.

    Hi

    Don't use

    Code:
    sudo pkill -9 .....
    unless it absolutely necessary. Try without the -9 (SIGKILL) and let it attempt to shudown normally.

    Code:
    sudo pkill ...
    BTW: When i checked that Dropbox link i had a 403 forbidden error.

    I'm glad you fixed it though

    Kind regards
    If you believe everything you read, you better not read. ~ Japanese Proverb

    If you don't read the newspaper, you're uninformed. If you read the newspaper, you're mis-informed. - Mark Twain

  10. #10
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    Re: [AMENDED] Ethernet connection not recognised.

    Hi Matt,
    Many thanks for the SIGKILL tip. I'm away at present but I'll use it when back in the shack.
    However, I did note that I had to use pkill each time I booted up Ubuntu, before I could obtain any connectivity.
    Is there no way of permanently resolving the issue, please?
    As for you obtaining the 403 forbidden error from DropBox, my apologies. I had omitted to obtain the public link and gave you my own link.
    It should have been: https://www.dropbox.com/s/xg88i5zr2ad72aa/NetPrint2.pdf
    Many thanks again, Matt, and kind regards,
    Roger

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