Hello,
By default eth0 is disabled in the stock Debian image because it makes the bootup really slow (it adds 60 secs) unless you have a network plugged in. Here's a fix for you:
1. Enable eth0 to come up automatically on bootup, by making sure you have the following lines in /etc/network/interfaces
auto eth0
iface eth0 inet dhcp
2. Now edit the dhclient configuration and make sure the following lines are uncommented and changed as below, using nano /etc/dhcp/dhclient.conf
timeout 10;
retry 15;
Reboot and if there's no network connected it'll only take 10 seconds longer. Also, the retry 15; means when you do plug a network in it should pickup a DHCP assigned IP within 15 secs rather than the default 5 mins!