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 how I workaround this:
1. Enable eth0 to come up automatically on bootup, by making sure you have the following lines using
iface eth0 inet dhcp
2. Now edit the dhclient configuration and make sure the following lines are uncommented and changed as below, using
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!