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I have a Linksys E900. I can access the internet and its admin page from Windows but not even its admin page from Ubuntu (on the same dual boot machine). Like there is no communication between the computer and the router when Linux is booted. I'm no networking expert but isn't TCP the same from Linux and Windows? How can there be any difference between the operating systems from the router's point of view? I have no networking issues on Ubuntu if I omit this router and I had used this same Ubuntu installation on the same machine with this exact same router for years before I moved. The only two differences I can think of are the modem and the router firmware which might be more up to date now (I reinstalled it). But I can't see how they can be relevant here.

Any advices are appreciated.

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  • What does ip addr show? Can you ping the router? What does the syslog say?
    – sebix
    Dec 13, 2014 at 12:33
  • are you using DHCP to obtain your IP address both on Windows and Linux? a possibility for this problem would be that Ubuntu is configured with a static IP address that is in the wrong subnet.
    – Ale
    Dec 13, 2014 at 12:37
  • There is no ip addr section for eth0. I cannot ping the router at all. Linux is configured to use DHCP. It actually does when I omit the router. As for the syslog, I'm not sure what I should be seeing. There are some DHCP entries related to an IP address in the range 10.0.5.x for another (I guess virtual) network interface but I can see no entries in the 192.168.x.x range for eth0 which would be what the router gives to my computer.
    – ooo
    Dec 13, 2014 at 13:08
  • Please post the output's @ooo . And all relevant configuration files, especially those changed by you.
    – sebix
    Dec 13, 2014 at 14:05
  • Output of what? Ifconfig? What are the relevant configuration files? I did not change any of them.
    – ooo
    Dec 13, 2014 at 14:13

1 Answer 1

Reset to default
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Ok, problem solved. This is one of the biggest WTF's of my history with computers. By the way, one problem with sites like ServerFault is that if people don't know the answer right away they will lose interest and one has to solve their problem alone anyway. Not complaining, just a thought.

So I tried to renew my IP using dhclient in verbose mode. DHCPDISCOVER messages were timing out so I was sure the problem had to be more fundamental. I used ethtool to check problems on the Ethernet level, and bingo. Link detected: no. This meant that the network card thought nothing was connected to it. No wonder DHCP didn't work. I unplugged the Ethernet cable from the router and plugged it directly into the modem. Link detected: yes! OK, now back into the router. Link detected: yes!! WTF? Connected the router to the modem. Link stat still: yes. Internet worked fine!

This is not the end of the story, though, because after a reboot I was disconnected again and had to redo the above process a couple of times to get it stable. Now everything seems to work.

Can someone explain this?

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  • Not complaining either, but your original question lacked any details that would help solve the issue... no ip addr nor ip link show outputs, no relevant dmesg entries, not even the model of the NIC.
    – user186340
    Dec 14, 2014 at 3:19
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    As for what can cause this, the usual suspects are a faulty connector or cable (and the Linux driver happens to be more sensitive to this than the Windows one) or a bad Linux driver (knowing the NIC's model would have helped).
    – user186340
    Dec 14, 2014 at 3:20

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