Reading bandwidth usage in MRTG or Cacti

Posted on 2009-02-19
Last Modified: 2012-05-06
I need help understanding bandwith usage graphs, actually just some clarification.

When looking at a graph from MRTG or Cacti of a WAN interface. If at a certain point Inbound is say 3Mb and Oubound is say 2.5Mb.
Total bandwith usage would be 5.5Mb?
And a 6Mb pipe would be almost saturated right?
Question by:mike_lfcu
    LVL 8

    Accepted Solution

    It depends on your connection and how it is hosted. If you have typical T1s and you say 6MB pipe I assume you have a 3XT1 meaning 3 bonded T1s. A typical T1 is 1.54MB Outbound and 1.54 Inbound. Do your 6MB or your 3XT1 is 6MB OUT and 6MB IN (not total combined)so you do not add the in and out traffic as they are independent.
    This is why the graph shows you both Inbound and Outbound as green and blue. From this sample you have not reached past 4MB in or out so it is not saturated...rather about 66% peak of your 6MB in or out and your average is way below.

    Author Comment

    We have a fractional-DS3 set at 6MB.
    LVL 8

    Assisted Solution

    That too will be as described above 6MB IN and 6MB out. Thanks, JW

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