[root@bigboy tmp]# cd /etc/sysconfig/network-scripts [root@bigboy network-scripts]# cat ifcfg-eth0 # # File: ifcfg-eth0 # DEVICE=eth0 BOOTPROTO=dhcp ONBOOT=yes [root@bigboy network-scripts]# As you can see eth0 will be activated on booting, because the parameter ONBOOT has the value yes and not no. You can read more about netmasks and DHCP in Chapter 2, "Introduction to Networking", that acts as a