Error: Missing Dependency: rrdtool = 1.2.27-3.el5 is needed by package rrdtool-perl

When I'm installing Ganglia on my CentOS, I've did the following:
# yum install rrdtool ganglia ganglia-gmetad ganglia-gmond ganglia-web httpd php

However, instead I got the followings
# Error: Missing Dependency: rrdtool = 1.2.27-3.el5 is needed by package rrdtool-perl

To workaround this issue, I've installed in stages. I'm assuming you have installed RpmForge Repository

# yum install rrdtool-perl
# yum install ganglia ganglia-gmetad ganglia-gmond ganglia-web httpd php

ok. It works.