Ubuntu

Ethernet shows as disconnected on new 12.04 installation

Asked by David Hartung

New Ubuntu 12.04 installation. Ethernet does not work, in fact the router does not even show the cable as being connected.
Wireless is also nonfunctional. To fix that I need to install firmware, which is easiest to install if I have an ethernet connection.

If it will help, I have this info:

leighann@LeighAnn:~$ sudo lshw -C network; lsb_release -a; uname -a; sudo rfkill list
[sudo] password for leighann:
  *-network
       description: Ethernet interface
       product: NetXtreme BCM5751 Gigabit Ethernet PCI Express
       vendor: Broadcom Corporation
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: eth1
       version: 01
       serial: 00:12:3f:15:58:e2
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm vpd msi pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion=3.121 firmware=5751-v3.29a latency=0 link=no multicast=yes port=twisted pair
       resources: irq:16 memory:dfdf0000-dfdfffff
  *-network
       description: Network controller
       product: BCM4318 [AirForce One 54g] 802.11g Wireless LAN Controller
       vendor: Broadcom Corporation
       physical id: 3
       bus info: pci@0000:03:03.0
       version: 02
       width: 32 bits
       clock: 33MHz
       capabilities: bus_master
       configuration: driver=b43-pci-bridge latency=64
       resources: irq:17 memory:dfcfe000-dfcfffff
  *-network DISABLED
       description: Wireless interface
       physical id: 2
       logical name: wlan2
       serial: 00:14:a5:04:b7:8d
       capabilities: ethernet physical wireless
       configuration: broadcast=yes driver=b43 driverversion=3.2.0-29-generic-pae firmware=N/A link=no multicast=yes wireless=IEEE 802.11bg
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.1 LTS
Release: 12.04
Codename: precise
Linux LeighAnn 3.2.0-29-generic-pae #46-Ubuntu SMP Fri Jul 27 17:25:43 UTC 2012 i686 i686 i386 GNU/Linux
0: phy0: Wireless LAN
 Soft blocked: no
 Hard blocked: no

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Revision history for this message
actionparsnip (andrew-woodhead666) said : 		#1

If you run:

sudo dhclient3 eth1

Does it get an IP address?

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David Hartung (david-lemagroup) said : 		#2

No, I an the command, input the password and got nothing. The curser blinks a few times and then comes on steady, but does not return to any sort of prompt.

Revision history for this message
actionparsnip (andrew-woodhead666) said : 		#3

When you type your password you will get no feedback. Or do you mean after the password entry?

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David Hartung (david-lemagroup) said : 		#4

I type the password, push enter and the cursor blinks about ten times and comes on steady.

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actionparsnip (andrew-woodhead666) said : 		#5

Have you checked the connection on both sides of the wire. Unplug and replug it in. YOu should hear a solid thunk as it goes in

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David Hartung (david-lemagroup) said : 		#6

yes, and I have also used the cord on another machine. The cord and the port on the router are fully functional. The Ethernet cord is also firmly seated in the machine Ethernet receptacle.

Revision history for this message
actionparsnip (andrew-woodhead666) said : 		#7

Try:

sudo ifconfig eth0 mtu 1500
sudo dhclient eth0

Source:
http://ubuntuforums.org/showthread.php?t=984675

Revision history for this message
David Hartung (david-lemagroup) said : 		#8

I am ran sudo ifconfig eth0 mtu 1500 and received this response: SIOCSIFMTU: No such device.

The machine sees the Ethernet port as eth1, not as eth0. Before changing your suggested commands to reflect eth1, I have a question. Is it possible that this is a part of the problem? As I understand, Ethernet port numbering always begins with 0. is the lack of an eth0 causing the software to no look further?

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actionparsnip (andrew-woodhead666) said : 		#9

sudo ifconfig eth1 mtu 1500
sudo dhclient eth1

As yours is eth1.

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David Hartung (david-lemagroup) said : 		#10

Thank you for all your help, but it seems that my problem is bad hardware. The machine I am trying to get working has been used exclusively in a wireless environment for the last 3 1/2 years. I have a copy of 12.04 on a stick, which I used to boot the machine as a test. Once the USB copy booted up, there was still no sign that the router even saw the computer. I took that same USB copy, used it to boot the machine I am using for these posts, and the Ethernet connection came up just fine.

The problem with the wireless connection seems to be a firmware issue and I was going to use the Ethernet connection do download firmware for the wireless adapter.

Again thanks.

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