I am running Debian testing (amd64) and after running an aptitude update/upgrade my wired network stopped working. I get a cable unplugged message. The cable is OK and the router is OK and the link pulses are there. My wireless is still working.

My system:

Linux version 3.1.0-1-amd64 (Debian 3.1.8-2) (ben@decadent.org.uk) (gcc version 4.6.2 (Debian 4.6.2-11) ) #1 SMP Tue Jan 10 05:01:58 UTC 2012

My onboard NIC is 

Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03)

I get this from dmesg

[ 1.325223] eth0: Identified chip type is 'RTL8168D/8111D'.
[ 19.611230] r8168: eth0: link down
[ 19.611925] ADDRCONF(NETDEV_UP): eth0: link is not ready

i tried downloading the latest drivers (r8168-8.035.00) from Realtek, compiled them and installed (./autorun) and got these messages:

root@orca:~/REALTEK/r8168-8.035.00# ./autorun.sh

Check old driver and unload it.
rmmod r8168
Build the module and install
Warning: you may need to install module-init-tools
See http://www.codemonkey.org.uk/docs/post-halloween-2.6.txt
DEPMOD 3.1.0-1-amd64
WARNING: could not open /lib/modules/3.1.0-1-amd64/modules.builtin: No such file or directory
load module r8168
Updating initramfs. Please wait.
update-initramfs: Generating /boot/initrd.img-3.1.0-1-amd64
WARNING: could not open /var/tmp/mkinitramfs_H9e5XM/lib/modules/3.1.0-1-amd64/modules.builtin: No such file or directory
Completed.

I read the reference on codemonkey, but it only talks about 2.4 and 2.6 kernels, so not sure if it is relevant. There was a bug in March regarding the missing file/directory, but the maintainers claim it was fixed. It is also just a warning, so not sure if it is relevant.

lsmod shows:
Module Size Used by
r8168 235362 0

ifup eth0 gives
RTNETLINK answers: File exists
Failed to bring up eth0.

ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:24:e8:fa:3a:aa
inet addr:192.168.25.150 Bcast:192.168.25.255 Mask:255.255.255.0
UP BROADCAST 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:45 Base address:0x8000

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:992 errors:0 dropped:0 overruns:0 frame:0
TX packets:992 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:79712 (77.8 KiB) TX bytes:79712 (77.8 KiB)

wlan0 Link encap:Ethernet HWaddr 00:24:d6:4d:f4:5c
inet addr:192.168.25.206 Bcast:192.168.25.255 Mask:255.255.255.0
inet6 addr: fe80::224:d6ff:fe4d:f45c/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:369882 errors:0 dropped:0 overruns:0 frame:0
TX packets:200219 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:238476416 (227.4 MiB) TX bytes:61312210 (58.4 MiB)

/etc/network/interfaces

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
#allow-hotplug eth0
NetworkManager#iface eth0 inet dhcp
auto eth0
iface eth0 inet static
    address 192.168.25.150
    netmask 255.255.255.0
    gateway 192.168.25.1
    dns-search tc.ph.cox.net
    dns-nameservers 68.2.16.25 68.2.16.30

Thanks for any suggestions you may have.

Mark