[mrtg] Issues with Integer size when adding multiple interfaces

Steve Baxter steve at pipenetworks.com
Sun May 25 05:05:39 MEST 2003


I am using MRTG version 2.9.17 on Redhat 7.3.

I am coming across an interesting problem, in one of my configs where I use the 
'+' operator to add together several interfaces (33 interfaces actually) when 
the combined data rate reaches about 14M BYTES /sec it seems to go crazy and 
loop around to zero or similar.

I have a attached a resultant image of what it looks like when it happens. The 
time around wednesday is evidence of what I am talking about.

I am really confused on this one, I assume that MRTG can handle more than 
14MBYTES/sec so I thought it may be that the addition logic limits the range 
of the values that can be added. 14MBYTES is really close to 2^30 bits.

I seem to get accurate graphs up to the point where it goes past about 

An advice would be appreciated.



Stephen Baxter
Director - PIPE Networks
phone : 07 3220 1100/ 0417 818 695
fax   : 07 3220 1800

PIPE Networks/IX Services Australia disclaimer 

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