Ubuntu 11.10 and Realtek (RTL8111/RTL8168) NIC driver problem

Finally, I figured out the problem that I had with network connection. The problem was with Realtek (RTL8111/RTL8168) NIC, which somehow detected differently by ubuntu 11.10 and uses r8169 kernel module driver.
To be sure, do check your NIC using:
$ sudo lscpi

You should see something like ...Realtek (RTL8111/RTL8168)...
Next step is to remove the r8169 module using:
$ rmmod r8169

If necessary install build-essential, etc:
$ sudo apt-get install build-essential linux-headers-$(uname -r) linux-source

Then, download the proper driver for that particular NIC from here. The file name should be something like r8168-8.027.00.tar.bz2.
Uncompress the file, and run the shell script file, as root:
# ./autorun.sh

Check the newly compiled driver:

$ sudo lsmod | grep r8168
$ ifconfig -a


Blacklist the r8169 module driver, by editing /etc/modprobe.d/blacklist.conf, add:
#blacklist r8169 driver
blacklist r8169

Reboot your system if necessary.

Configure DHCPd to Work on Certain NIC(s)

Your server has more than one network interfaces and you need DHCP server to associated with only one of them.

Here is how you configure it on Ubuntu:

# File: /etc/default/dhcp3-server
INTERFACES="eth0"
or
INTERFACES="eth0 eth1"

Onn Redhat/Fedora/Centos:
# File: /etc/sysconfig/dhcpd
DHCPDARGS=eth1
or
DHCPDARGS="eth0 eth1"

Reference:
http://www.centos.org/docs/5/html/Deployment_Guide-en-US/s1-dhcp-configuring-server.html

Permanently Set Network Interface Speed, Duplex or Auto Negotiate Settings on Linux

On RedHat (based) Linux:

Edit /etc/sysconfig/network-scripts/ifcfg-eth0 file for eth0 interface.
On my Fedora15, the file looks like the following:
/etc/sysconfig/network-scripts/ifcfg-Auto_wlan

So, open the corresponding file according to your need, then append the following line:
ETHTOOL_OPTS="speed 100 duplex full autoneg off"

Save the file, and restart network interface by executing the following command:
# /etc/init.d/network restart

The previous example is for setting the NIC to 100Mbps, full duplex and no auto negotiation.


If you want 1000Mbs use the following configuration:
ETHTOOL_OPTS="speed 1000 duplex full autoneg off"

or

ETHTOOL_OPTS="speed 1000 duplex full autoneg on"

For Ubuntu and perhaps Debian and other Debian based Linux, edit /etc/network/interfaces, and add pre-up statment, so it will look like something like the following:

auto eth0
iface eth0 inet static
pre-up /usr/sbin/ethtool -s eth0 speed 1000 duplex full

Refer to this link for more information.

For Ubuntu:
Edit /etc/network/interfaces and add the following line:
pre-up /usr/sbin/ethtool -s $IFACE autoneg off 100 duplex full