[mrtg] In or Out?

Jay Hennigan jay at west.net
Tue Dec 2 23:46:01 CET 2008

Kevin Wong wrote:
> Hi Everyone, can someone clarify which traffic is IN or OUT?
> I'm monitoring traffic at subnet B from subnet A (where MRTG runs).  My 
> understanding is this: the IN would be traffic entering router at Subnet 
> B, and OUT would be the traffic leaving.  And if this is true, then the 
> reverse would be apply to Subnet A.

It is from the respect of the monitored interface.

If you are looking at an interface on router A, then traffic flowing 
over the wire towards that interface is "IN", and traffic leaving the 
interface toward the wire is "OUT".

Your use of "subnet" is somewhat confusing in this context.

If you have two boxes A and B, and MRTG is running on A, then traffic 
from A to B is "OUT" (it is leaving A) and traffic from B to A is "IN".

If you want to reverse this, you can place a minus sign (-) in front of 
the target.

See:  http://oss.oetiker.ch/mrtg/doc/mrtg-reference.en.html

Search for "Reversing".

Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
Your local telephone and internet company - 805 884-6323 - WB6RDV

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