rpm --import http://download.openvz.org/RPM-GPG-Key-OpenVZ
yum install ovz-kernel-PAE
Now remember to set /etc/sysctl.conf to "net.ipv4.ip_forward = 1"
You can apply the change immediately by running
sysctl -w net.ipv4.ip_forward = 1 but remember that you still have to set sysctl.conf
sysctl -p will load and apply any changes to sysctl.conf as well