yum through proxy with authentication, username & password proxy support

See the Basic setting & then try to apply the following ---

http_proxy="http://username:passwd@192.168.1.1:3128" /* if PROXY host is http://192.168.1.1 & PROT is 3128 */
ftp_proxy="http://username:passwd@192.168.1.1:3128"

Don't forger to export the environment variables!!!!!