Easy way to graph the sum of the same OID on several hosts

[dwsmall]

I have the OID that represents the number of active connections on a firewall at any given moment. I need a single graph that shows the sum of all those values. Could I use CDEF to do this somehow? Is there another way to sum the data from the different RRD files? Or am I just better off writing a script and graphing the output of that?

[gandalf]

Please see AGGREGATE plugin and study the PDF provided to find how to implement your use case
R.