For some reason, every time I start up my computer I have to "ifup eth0" to get connected to the internet. I have no idea why I have to do this now. The only thing that has changed is the physical location of the computer. I moved from one house to another, transferring the same cable connection with the same ISP (DHCP, not static IP). I have the same modem, router, etc. During startup, there is no indication that bringing up network services does not get an IP address, but I still have to go into a terminal window every time I boot and ifup eth0.

Any ideas?

ok first go to /etc/sysconfig/networking-scripts/ in here will be a file called ifcfg-eth0 edit it. then find the line ONBOOT = no ; change the no to a yes and that's it.

Everything is already set to startup on boot.

Ok, you were right. I checked that anyways and it was set to no. I have no idea how it got that way, but it works perfect now.