[rrd-users] Re: if*Octects counter reset

[Alex van den Bogaerdt]

Max Gargani wrote:

> I'm trying to use rrd+orca to graph bandwitdh usage on cisco's router. The
> problem is when ifInOctects and ifOutOctects reach 4G the counters are
> resetted restarting from 0. This cause a wrong graphic.

Do you really mean "resetted restarting from 0" or do you mean the
counter increments like 4294967290 + 12 == 6 ?

If the counters really reset, there's something wrong on the Cisco
(but I doubt that).  It is more likely that the counter just wraps.

RRDtool is designed to handle these wraps.  Unless a counter increases
with more than (2^32-1) RRDtool will be able to handle this increase.
This BTW is 14.3 MBps or 114.5 Mbps when you poll every 5 minutes.

If you need to monitor an interface that can handle higher bandwidths
and you cannot use the 64-bit counters, lower your polling interval
to an appropriate value.  Example for 155 Mbps:  (2^32*8)/(155*10^6)
== 221.7  --> set your interval to 3 minutes (180 seconds) which is
lower than 221.

I don't use orca so I don't know it.  Perhaps orca is regarding wraps
as if they are resets?  If so, it will insert "U" each time the counter
wraps and you will notice gaps in your images.

Handling wraps this way is good to prevent false readings from counters
that increment with values just over 2^32.  This would otherwise result
in very low rates such as 1 Mbps when the actual rate would be 115.5

Lowering your polling interval will help a bit in this case but you
would still suffer from the unknowns being inserted.  If you cannot
use the 64-bit counters and if you cannot configure orca to allow the
wraps (assuming it really is orca) there's no other option than to
a) live with it
b) use another tool to collect the data
c) use another tool altogether

HTH
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