I have been trying connect to the internet in Fedora Core 10 via a Motorola Surfboard 5101 cable modem with no success. Comcast is my ISP. I have an RTL8111/8168B PCI Express Gigabit Ethernet controller.
The ethernet cable is detected and a connection attempt is made but after about a minute it stops and says "the network connection has been disconnected.
I tried changing the ./ifcfg-eth0 file to:
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=dhcp
USERCTL=no
IPV6INIT=no
NM_CONTROLLED=no
TYPE=Ethernet
PEERDNS=no
HWADDR=00:1e:46:af:9b:62 (the hfc mac address on my modem)

This did not connect to the modem.
I changed the network configuration settings by setting the mac address for eth0 in the "Network Configuration" user interface and this actually connected to the modem (but not to the internet). When I plugged the cable in another computer to look up something and then switched it back to the computer running fedora core it stopped working again, despite changing the network configuration settings, and is still giving me the "network connection has been disconnected" message.

I do not know how to configure this to connect to the modem, let alone the internet.

try

NM_CONTROLLED=yes

if network manager is installed it gets fussy if it cant control the NICs