This is guidance for those with integrated Realtek RTL8111 series gigabit Ethernet, built in to motherboards such as the ASRock G41M-LE.

Ubuntu 8.10 (and may other versions) have been reporting problems with connectivity. Here is the solution in a walk-through format. You must be root (sudo su -).

1) Check to see if the r8169 module is loaded
-> lsmod | grep r816
r8168 41104 0 
-> lspci -v
01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03)
Subsystem: ASRock Incorporation Device 8168
Kernel driver in use: r8169
Kernel modules: r8169

2) Download the official Realtek driver
Realtek RTL8111/RTL8168

3) Remove the r8169 module
-> rmmod r8169
-> mv /lib/modules/`uname -r`/kernel/drivers/net/r8169.ko ~/r8169.ko.backup
( the ` is a backtick, it is not an apostrophe or single quote )

4) Build the new r8168 module for the kernel
-> bzip2 -d r8168-8.009.00.tar.bz2
-> tar -xf r8168-8.009.00.tar
-> cd r8168-8.009.00
-> make clean modules
-> make install

5) Rebuild the kernel module dependencies
-> depmod -a
-> insmod ./src/r8168.ko

6) Remove the r8169 module from initrd
-> mv /initrd.img ~/initrd.img.backup
-> mkinitramfs -o /boot/initrd.img-`uname -r` `uname -r`

7) Add r8168 module to /etc/modules
-> echo "r8168" >> /etc/modules

8) Reboot, You are done!

9) Examine that ONLY the r8168 module is loaded for the interface
-> lspci -v
01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03)
Subsystem: ASRock Incorporation Device 8168
Kernel driver in use: r8168
Kernel modules: r8168