Using yum behind a proxy

I was recently attempting to install a software on centos 5 and ran into an error with the yum install command as shown below:

Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=5&arch=x86_64&repo=os error was [Errno 4] IOError: <urlopen error (111, 'Connection refused')>

Setting the http_proxy did not help matters. I found documentation on forums that suggested adding the line proxy_http=http://proxy:port in /etc/yum.conf. That still did not help. I finally came across a post on centos forums that suggested that the setting to be made in /etc/yum.conf is actually proxy=... and not http_proxy=...