[mrtg] Re: Total bandwidth usage

Peter Glanville peter_glanville at cuk.canon.co.uk
Thu Apr 10 18:43:12 MEST 2003

>Am I correct in assuming that if MRTG graphs 80k on input and 80k on
>I am actually using 160k of my network connection?
>If I am correct can I create a graph that displays the 160k of actual
>instead of splitting the usage up into input and output?

My understanding of a full duplex ethernet network was that a 100megabit
network would shift 100Mb (=12.5MB) in each direction at the same time. So
no, you do not want to add them together.
If you have a 10Mb half-duplex system it can do 10Mb in OR out, but packet
collisions result from trying to do both at the same time. So then adding
the figures together would have some sort of meaning, but I would not
Asynchrounous systems (eg Broadband in the UK) will shift 500kb one way and
128Kb the other. So you certainly do not want those added together!

If you want a third line on the graph representing total In + total Out,
you will be pushed under just MRTG, but upgrade to use RRD to store your
data and use a front end such as Routers2.cgi to view your data. Front ends
often have a totalling feature built in.


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