Yum Update

I am using Cent OS 5 i need to update proxy server address in yum, i don't know where to update and how exactly i need to specify the proxy address can anyone help me in the issue.

Have a look at this post from another forum and see if it works for you: RESOLVED: how to configure yum to get through proxy? - FedoraForum.org

you can read this page for more stuff:Setting network options and proxy