[CentOS] How does a linux DHCP machine inform DNS of its name and obtained address

Wed Feb 1 03:06:53 UTC 2012
Jerry Geis <geisj at pagestation.com>

I am using a number of DHCP devices on a network. Working fine with 
CentOS  5 x86_64.
My question is now how do I tell the DNS (after I get my DHCP address) 
about my devices
name and IP address so that others can find me by my machine name?

I thought that was an automatic thing - but it appears not.