Can't connect to internet using DHCP and cable modem

Question

I'm new to Linux but liking it so far. My symptom is that I have a machine which dual boots WinXP and Ubuntu -- internet works on WinXP, not on Ubuntu.

Some specs: Ubuntu 11.10; AMD Athlon 64 processor; Network Interface Card by Realtek (RTL-8139/8139C/8139C+); cable modem by Scientific Atlanta (2100R2).

The connectivity is Cable > Modem > PC (by DSL)

The first times I booted into Ubuntu from CD, could not connect to internet. After installing on HDD, and booting (not from CD), internet worked once, and never again.

Searching around, I decided to try editing /etc/network/interfaces

Used to read:

auto lo
iface lo inet loopback

Based on posts, I decide to change it to

auto lo eth0
iface eth0 inet dhcp
iface lo inet loopback

and run sudo /etc/init.d/networking restart

This gives me a message about the command being deprecated, and then hangs so I kill it. I reboot and now in the splash screen I see "Waiting for network configuration" then "Waiting up to 60 seconds for network configuration" then "Booting without full network configuration".

Reading more online, I decide to keep /etc/network/interfaces the same, and edit file /etc/NetworkManager/NetworkManager.conf:

[main]
plugins=ifupdown,keyfile

[ifupdown]
managed=true    # It was originally false

This changed nothing.

When I run the command ifconfig -a:

eth0    Link encap:Ethernet  HWaddr 00:14:2a:03:f0:77
    inet6 addr: fe80::214:2aff:fe03:f077/64 Scope:Link
    UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
    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)
    Interrupt:22 Base address:0xdf00 

eth0:avahi Link encap:Ethernet  HWaddr 00:14:2a:03:f0:77  
      inet addr:169.254.7.133  Bcast:169.254.255.255  Mask:255.255.0.0
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      Interrupt:22 Base address:0xdf00 

lo        Link encap:Local Loopback  
      inet addr:127.0.0.1  Mask:255.0.0.0
      inet6 addr: ::1/128 Scope:Host
      UP LOOPBACK RUNNING  MTU:16436  Metric:1
      RX packets:488 errors:0 dropped:0 overruns:0 frame:0
      TX packets:488 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:0 
      RX bytes:38880 (38.8 KB)  TX bytes:38880 (38.8 KB)

I find it weird that I have no inet address for first entry for eth0, and why two entries? Actually, I don't know if that's unusual. Reading further, I decided to try to force a static ip address, you can tell me if that makes no sense. I changed /etc/network/interfaces to read:

auto lo
iface lo inet loopback
address 127.0.0.1
netmask 255.0.0.0

auto eth0
iface eth0 inet static
address 192.33.137.200
netmask 255.255.255.0
gateway 99.241.122.1

and reboot. This didn't help a bit. Been searching everywhere. DHCP is supposed to just 'work'. What else to do?

A bit more info: when I run route:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         *               0.0.0.0         U     1002   0        0 eth0
link-local      *               255.255.0.0     U     0      0        0 eth0

And when I run sudo lshw -class network:

*-network
   description: Ethernet interface
   product: RTL-8139/8139C/8139C+
   vendor: Realtek Semiconductor Co., Ltd.
   physical id: 5
   bus info: pci@0000:02:05.0
   logical name: eth0
   version: 10
   serial: 00:14:2a:03:f0:77
   size: 10Mbit/s
   capacity: 100Mbit/s
   width: 32 bits
   clock: 33MHz
   capabilities: pm bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation
   configuration: autonegotiation=on broadcast=yes driver=8139too driverversion=0.9.28 duplex=half latency=64 link=yes maxlatency=64 mingnt=32 multicast=yes port=MII speed=10Mbit/s
   resources: irq:22 ioport:df00(size=256) memory:fddff000-fddff0ff

Well, I am mucking around in things I don't understand. Time to ask: any help is much appreciated! I am teachable.

Answer 1

Looking around there have been many problems and few solutions with the RTL8139 NIC. Tried many many things and finally got it working. I believe only the last step I performed worked, but I don't know for sure so I include all steps below.

Based on advice at http:[double-forward-slash][triple w].question-defense.com/2010/06/03/ubuntu-10-4-eth0-not-available-rtl-81398139c8139c-rev-10, I ran the following commands:

sudo mii-tool eth0 -F 10baseT-FD
sudo rmmod 8139too
sudo modprobe 8139too

Commands seemed to do something, but no output to the terminal. But no luck, so tried things from http://forums.fedoraforum.org/archive/index.php/t-1679.html, and ran commands:

sudo ifconfig eth0 down
sudo rmmod 8139too
sudo insmod 8139too media=0x01

I got a complaint on running the last one, something about "8139too file not found", which makes sense -- I guess rmmod means remove module; and having run lsmod | grep 8139 before and after all the above commands, indeed, where I had two entries (including one for 8139too) I was left with only one entry (which starts with 8139cp).

But, still no luck.

Finally, following advice at http://ubuntuforums.org/showthread.php?t=1773402, I booted into Windows XP, and did the following Right click My Computer > Hardware > Device Manager; Expand the network interface card section and double click the Realtek one; Look around for "Wake-on-lan after shutdown" option, and set to "enabled"; Reboot into Linux

!!WORKED!! 8)

Answer 2

I think your system is loading the wrong driver. A solution to this problem might be here : http://kopiteforlife.wordpress.com/2012/05/01/recovering-from-ubuntu-12-04-lts-upgrade-failure-from-11-10/