Installing epel repo on CentOS

http://incubator.apache.org/ambari/1.2.1/installing-hadoop-using-ambari/content/ambari-chap2.1.2.html

says:
Install the epel repository:

yum install epel-release

Which is wrong, the repo has to downloaded first, as example version 6:
wget http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
sudo rpm -Uvh epel-release-6*.rpm