Seems odd to me that it fails to work.
First you should not need DHCP Daemon running. You are getting an IP from cable provider.
Second do you have a firewall setup and running. If so turn it off tempoary to see it you get a connection. To remove firewalls rules in a terminal with root access type ' ipchains --flush ' Now see if you can browse. If so then the firewall rules need edited.
Most cable modem setup's I have seen use the MAC address ( A hardware address code on the the nic card in a 12 digit code ) of the nic card to authenticate with. So if you have not changed the nic from the when your cable modem was installed then it should still see the correct MAC address of the card. The card should have the MAC address on it somewhere.
Lets see what you have in /etc/sysconfig/network-scripts/ifcfg-eth0
also contents of /etc/resolv.conf. This contains DNS numbers.
Now verify the HWADDR matches the MAC address on the nic. If that is correct then I am at a lost here.
You can get DNS numbers from your provider and hardcode them in to /etc/resolv.conf
Try to ' ping -c5 18.104.22.168 ' That is google website. If you get a reponce then in your web browser type ' http://22.214.171.124
' in the address bar and see if it diplays the website. If it does then something about DNS is not working. You can get DNS numbers from your provider and hardcode them in to /etc/resolv.conf
Sample of my /etc/sysconfig/network-scripts/ifcfg-eth0
Worst case to get you back up is to buy a cable/dsl router and set it up between your modem and linux box. You need to make the router imatate the MAC address used when the cable modem setup was done. Most of these little cheap routers I have used are quite easy to setup.