[rrd-users] Collecting from cell counters

Maarten van Gelder mvgelder at vt.edu
Mon Oct 30 20:14:35 MET 2000

Question first, explanation later.

Question:  How does one deal with cell counters when using RRD tool as
backend to MRTG and one wants to display traffic in bytes or bits?

Explanation:  I have been polling cell counters of Fore ASX-1000 switches
for quite some time with MRTG, first using the log files and later
migrating to RRD tool.  When using the log files, I would multiply the
counter value by 53 (in the Target field of the MRTG config file) so
traffic would be displayed in bytes.  When migrating to rrdtool I
discovered that that was no longer possible.  If I read the documentation
right, RRD tool will detect counter wraps and compensate for it AND know
whether dealing with a 32 bit or 64 bit counter.  Multiplying a 32 bit
counter by 53 before sending it to RRD tool suggests to RRDtool that the
counter is 64 bit.  When a counter wrap occurs on the device, RRDtool
assumes the a 64 bit counter wrapped.  Tell me if I am wrong, but I think
that even adding two or more 32-bit counter values (like adding interfaces
that belong to the same VLAN) will have this result.  I have added a
'celltobit' option to MRTG's config (and to 14all.cgi) to deal with
cell-based counters but customizations are inconvenient when upgrading.
Anyone on this list who is collecting cell counters has any suggestions?


Maarten van Gelder
mvgelder at vt.edu

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