mrtg xymon integration problem

list Pavel Traian
Fri, 17 Feb 2012 07:30:07 -0800 (PST)
Message-Id: <user-8c5642272420@xymon.invalid>

Hi,
I have installed Xymon server on a CentOS 6 x64.
I wanted to integrate MRTG into it and i got an error.
After i add the below lines: 

# For Xymon integration
WorkDir: /var/lib/xymon/rrd
LogFormat: rrdtool

I get this error:

ERROR: could not find RRDs.pm. Use LibAdd: in mrtg.cfg to help mrtg find RRDs.pm

The problem is that i don't know where to find RRDs.pm. 
Regards.