Can not obtain an IP address via DHCP on new system. Why?

[Tom H]

On Sun, Mar 6, 2011 at 9:46 PM, Jay Ridgley <jridgley2 at austin.rr.com> wrote:
>
> OK, I must be stupid. I have tried to get this new system up yet I keep
> failing to obtain an IP address via DHCP from my provider. I have the
> following configuration.
>
> /etc/network/interfaces:auto lo
>
> iface lo inet loopback
>
> # Connection to Time Warner Cable
> # Internal RJ45 port
> iface eth0 inet dhcp
>
> auto eth0
>
>  --snip--
>
> /etc/dhcp3/dhcpd.conf:
>
> ddns-update-style interim;
> ignore client-updates;
>
> # DHCP for eth0 - outside world connection via cable modem
> #  no entries here
>
>  --snip--
>
> All systems that are behind the firewall work fine except for going outside
> my local network (expected, since I have no connection on the firewall).
> When I boot the new system ifconfig does not show eth0. Yet it is there and
> plugged into the cable modem. The information does show in an lspci.

1. "/etc/dhcp3/dhcpd.conf" is the config file for a dhcp server.

2. You shouldn't add

auto eth0
iface eth0 inet dhcp

to "etc/network/interfaces" if you're using Network Manager.