Hello, I'm trying to graph a couple of packet over sonet sdh interfaces on two cisco 7200 routers and I'm not getting the correct graph. Everything is fine until the traffic starts to go over 120 megabits/sec. At that point the graph dips and shows that traffic is down to less than a few megabits. I believe that this is a counter wrapping problem where any values over a certain value are being interpreted as low values. for example if the max of a graph is 120, then when the traffic hits 125, it draws 5 (125-120). I don't know if this is in fact what's happening but I really need to fix this. I've even modified the maximum value in the data sources page to be 9155000000 instead of the usual 100000000. I've tried queriying with 64 bit counters but then I don't get any results on the snmp querry. Please let me know if you know how to fix this.
Much appreciated,
Emi.
Packet Over Sonet not graphing right.
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Yes, it is related to counters wrapping. Since by default you poll 32-bit counters every 5 min this means that max speed you can measure is 2^32/300 bytes/sec = 14316557 bytes/sec = 114532456 bits/sec what is less than 120 Mbps. When you exceed this speed rrdtool gets confused and you see it jumping up and down.
The solution is to use 64-bit counters. Remember however that you need to use SNMP version 2 (2c) or 3 to poll such counters. You failed with polling probably because you used version 1. Remember also that PHP built-in SNMP support does handle only version 1. This means you need to turn it off and use external net-snmp tools instead.
Setting so high maximum value does not make much sense. Just use your interface speed in bytes/sec units. One remark - cacti in current version can't change maximum value in existing rrd file (even if you see it changed in web GUI). You need to delete coresponding rrd file after this change and let cacti create new rrd file.
- bulek
The solution is to use 64-bit counters. Remember however that you need to use SNMP version 2 (2c) or 3 to poll such counters. You failed with polling probably because you used version 1. Remember also that PHP built-in SNMP support does handle only version 1. This means you need to turn it off and use external net-snmp tools instead.
Setting so high maximum value does not make much sense. Just use your interface speed in bytes/sec units. One remark - cacti in current version can't change maximum value in existing rrd file (even if you see it changed in web GUI). You need to delete coresponding rrd file after this change and let cacti create new rrd file.
- bulek
thanks.
Hello,
Thanks for your help. I unintstalled php_snmp and now the querries take 3-4 times longer each, raising the processing time from 20 seconds to 167 seconds. Is there any other way of polling 64 bit counters with php_snmp or with some other method? Also we would really like to be able to base the 95 percentile based on the greater of input or output and not the sum of both. Is this possible without making two graphs for each interface?
Thanks for your help.
Emi.
Thanks for your help. I unintstalled php_snmp and now the querries take 3-4 times longer each, raising the processing time from 20 seconds to 167 seconds. Is there any other way of polling 64 bit counters with php_snmp or with some other method? Also we would really like to be able to base the 95 percentile based on the greater of input or output and not the sum of both. Is this possible without making two graphs for each interface?
Thanks for your help.
Emi.
Same issue
I know this is a old topic but I am having the exact same issue... I have change to 64 bit counters and I am running version v2c on my Foundry NetIron.....
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