bandwidth usage report

Unanswered Question
Jun 21st, 2009
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I am seeing a strange problem with bandwidth usage reports.mrtg for one of the links shows different readings for input & output interfaces.

For eg. if inside interface graph shows 4 Mbps usage, outside interface for same duration shows much less than that.

Strangely this occurs only at certain times.Otherwise it seems fine.

I cross checked this with another tool which shows near correct usage.

Please advice.


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Overall Rating: 3 (2 ratings)
Giuseppe Larosa Sun, 06/21/2009 - 11:36
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Hello Sunny,

32 bit wide MIB interface counters can be affected by wrapping:

the graph points are calculated using the difference of last and penultimate reading.

But the octets variable can fill the 32 bits integer because it acts as an accumulator, and so sometimes the new value is actually smaller then the penultimate value.

Hope to help


suthomas1 Mon, 06/22/2009 - 06:22
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Thanks Giuseppe.

Any ways to overcome this & any specific links to learn more about it.

Appreciate your help!

Giuseppe Larosa Mon, 06/22/2009 - 07:17
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Hello Sunny,

some platforms support 64 bit counters that have an HC in the name

ifinoctets = 32 bit counter

ifHCinoctets = 64 bit counter

Object ifHCInOctets


Type Counter64

Permission read-only


Hope to help


suthomas1 Sun, 06/28/2009 - 06:34
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Thanks Giuseppe,my interface is fastethernet and router is 2811.

Does it support 32 or 64bit counters & how can we derive what interface supports how much bits?

By the docu you provided it seems to be affect of wrapping, but then am puzzled at how another monitoring tool gave pretty accurate reading for same time.

Appreciate your help.


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