[mrtg] Re: stupid question

[Merton Campbell Crockett]

On Fri, 6 Oct 2000,  Domain Reg. @meganet.net wrote:

> 
> Don't mean do be stupid but could someone explain in detail what mrtg
> considers incoming/outgoing traffic. I assume incoming means traffic going
> to your net work, tcp, http etc and outgoing is form your network to the
> internet (lan to wan). Forgive me if I sound confused.

Most routers and hubs report traffic from the perspective of the interface
being monitored or managed.  Incoming traffic is moving from the external
transport media through the interface adapter to an internal buffer, bus,
crossbar, etc.  Outgoing traffic is simply moving in the opposite
direction.

While a reasonable way of referencing information at the hardware level,
it is often confusing to the human who tends to view the flow in terms of
one network to another.  Some people have a difficult time comprehending
that the traffic that they are interested in is the transmit data on Port
1 of Router A and the received data on Port 1 or Router B.

Fortunately, MRTG provides a solution to this problem.  If you "negate"
the interface index number, it reverses the sense of the incoming and
outgoing counters.  This allows you to create a series of graphs that
provides a view of the traffic relative to human perception regardless of
interface viewed.

For example, on the ethernet port of a router that connects to your ISP
negate the index of the ethernet interface.  After doing this the graph
should look nearly identical to the graph for the serial link to your
ISP.  Any difference in traffic volumes will be the result of filters on
the router that restrict what packets can cross the network boundary.

Merton Campbell Crockett



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