I just installed ubuntu 12.04.1 alternative install (for raid 0 on some disks). I Have some problems with the net. I'm at school, we use cable, and it got IPv6.

If I run ifconfig eth0 heres my output:

eth0      Link encap:Ethernet  HWaddr e0:cb:4e:87:ff:db  
          inet addr:128.39.194.217  Bcast:128.39.194.223  Mask:255.255.255.224
          inet6 addr: 2001:700:1100:8008:e2cb:4eff:fe87:ffdb/64 Scope:Global
          inet6 addr: fe80::e2cb:4eff:fe87:ffdb/64 Scope:Link
          inet6 addr: 2001:700:1100:8008:48f7:c23:1d87:da6c/64 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1063378 errors:0 dropped:0 overruns:0 frame:0
          TX packets:489811 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1577173461 (1.5 GB)  TX bytes:37043669 (37.0 MB)
          Interrupt:68 Base address:0x6000

My /etc/network/interfaces look like this:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface

auto lo
iface lo inet loopback
# The primary network interface
auto eth0
# NetworkManager#iface eth0 inet dhcp
# NetworkManager#hostname 2001:700:1100:1::4
# This is an autoconfigured IPv6 interface
iface eth0 inet6 auto

(I had to remove the hash tags, because of the BIGFONT i get on ask ubuntu)

The "network manager" says that I'm not connected.

Let me know if you need any more information. :)