If you have a DHCP server, make sure that your /etc/sysconfig/networking/ifcfg-eth0
file has the following contents:
And that your /etc/sysconfig/network
file has these contents:
Make sure you set the hostname to something. If you don't have a domain name, you can get a free dynamic IP compatible name from www.dyndns.org
and from www.dns2go.com
(dns2go actually has a Linux client). Linux doesn't work nicely without a valid hostname.
Once you get these set up, log in as root and type "service network restart". That will shut down your network interfaces (your ethernet card "eth0" and the loopback adapter "lo") and bring them up with the new settings. If you really have a DHCP server on your network, you should be up and running in no time.
You can always check your current set up by running /sbin/ifconfig