total traffic for multiple servers

[rmcclain]

I was asked to create a graph to sum the in and out traffic of a number of hosts and create a graph that is just their sum.. Does anyone have any pointers on how I can make that happen? The graph shouldn't have lines for the individual hosts.. it should basically be just like the normal traffic graph, only summed over a number of hosts.

Thanks!

[gandalf]

That'S doable. But no automatism. Requires some knowledge of cacti, so be prepared ...

First, I advertise my AGGREGATE plugin for a fast and convenient way to get all required rrd files into the graph. Doing so, please check each "Skip" checkbox with the exception for the original AREA/LINE item.
Yes, it does show individual lines for each host, but we will change it in a minute:
Now, create a CDEF that reads cdef=CURRENT_DATA_SOURCE,0,*
Apply this to all your AREA/LINEs to suppress them.
Next, create a CDEF that reads cdef=SIMILAR_DATA_SOURCES_NODUPS.
Create a new Graph Item, select a data source referring to any traffic_in item and associate it with the new CDEF. Apply a color and either AREA or LINE.
Now, do the same with traffic_out.
That's it.

I do not claim this to be very elaborated. If in doubt, please post last result as a screenshot (Graph Management, DEBUG mode)
Reinhard