Home / ubuntu / Questions / 6129
Accepted
Oscar Godson
Asked: 2010-10-12 12:44:57 +0800 CST

Why does my Ethernet port sometimes not work?

  • 772

I've noticed that my Ethernet port works fine once, but after it's disconnected and i connect to a wireless network and I go and try to plug the Ethernet port back in, it doesn't work until I reboot. Why is this?!

Also, the lights light up but it's like the Ubuntu doesn't see it. Is there a way to reboot the Ethernet port programmaticly through Terminal? I've also tried to delete and readd Auto Ethernet through the Network Preferences.

I have a Lenovo ThinkPad L512 with Ubuntu 10.04

==UPDATE==

I did the first step Maco said to do and here is what I got:

oscargodson@ubuntu:~$ sudo service network-manager stop
[sudo] password for oscargodson: 
network-manager stop/waiting
oscargodson@ubuntu:~$ sudo ifconfig eth0 up
SIOCSIFFLAGS: Cannot allocate memory
oscargodson@ubuntu:~$ sudo dhclient eth0
Internet Systems Consortium DHCP Client V3.1.3
Copyright 2004-2009 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

SIOCSIFFLAGS: Cannot allocate memory
SIOCSIFFLAGS: Cannot allocate memory
Listening on LPF/eth0/60:eb:69:02:50:f0
Sending on   LPF/eth0/60:eb:69:02:50:f0
Sending on   Socket/fallback
receive_packet failed on eth0: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 3
send_packet: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 4
send_packet: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 6
send_packet: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 11
send_packet: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 17
send_packet: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 17
send_packet: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 3
send_packet: Network is down
No DHCPOFFERS received.
No working leases in persistent database - sleeping.

I've tried everything Maco suggested and finally figured out my memory isn't low although I keep getting a SIOCIFFLAGS: Cannot allocate memory error. I have over 1GB of RAM free as we speak.

I found this page: http://www.linuxquestions.org/questions/linux-newbie-8/weird-ethernet-problem-838220/

And did what the person there said which was:

lspci| grep -i ethernet
dmesg | grep -i ethernet

And it gave me some output and the last command gave me:

r8169 Gigabit Ethernet driver 2.3LK-NAPI loaded

I then tried Maco's stuff again and i didn't get the error anymore, however, the Ethernet still doesn't connect although now it doesn't give me the memory allocation error.

10.04 networking lenovo hardware thinkpad

2 Answers

  1. Best Answer

    Sounds like bug. Lets dig in.

    First, stop Network Manager: sudo service network-manager stop

    Then, plug in the cable and bring up the interface sudo ifconfig eth0 up and tell it to ask for a new dhcp lease sudo dhclient eth0 (I'm guessing it's eth0, if not use the right name)

    Did it work? If so, file a bug on Network Manager: ubuntu-bug -p network-manager

    If not, try reloading the network driver. This should simulate a reboot to the ethernet port. To find out your driver, look in /etc/udev/rules.d/70-persistent-net.rules You'll see some bits like:

    # PCI device 0x10ec:0x8136 (r8169)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:f1:4c:01:94:3e", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

    Finding the one that matches your interface's name, look at what's in the parentheses where mine says r8169. That's your module's name.

    sudo modprobe -r r8169 && sudo modprobe r8169

    (replacing r8169 with your module's name) Try the dhclient step again. If that worked, I suspect it's a kernel bug. ubuntu-bug -p linux

    • 3

  2. I'm getting the same problem. Wireless works on boot provided router is switched on beforehand. If its not then I have to go through the process of setting up a network again. Wired connection refuses to work at all with the ifconfig: SIOCSIFFLAGS: Cannot allocate memory coming up. N.B. This is using BrowserLinux (based on Puppy Linux)

    • 0