Traffic graph highly inaccurate

[DutchSamurai]

Hello,

I'm new to Cacti so apologies if I'm asking the obvious but I've noticed the traffic graphs created by Cacti are not accurate at all, totally missing out on bandwidth generated in short bursts.

I want to use Cacti to graph the traffic going through the WAN interface on my PFsense box. I got the poller interval set to every 10 seconds and the cron interval to every minute under settings. I added the template Interface - Traffic as a data source and created the in/out Bytes (64bit counters) and in/out Bytes - total bandwidth (changed the data query to 64bit counters).

But the graphs that get created are totally inaccurate. Prolonged steady traffic gets logged fine but webbrowsing or short downloads (e.g 50MB in 20 seconds) don't get logged properly. No spike is shown and total added bandwidth consumed might increase with something like 20kb while in reality its 5MB.

I understand if there is lets say a 2 seconds 1MB/s spike that won't show up because it'll get averaged but I do need it to show the correct amount of data transferred otherwise I'll have no idea if the graph is actually reliable.

Is there anyway to do this? Seems like the traffic graph should do exactly that but somehow it doesn't.

[phalek]

Ask in the pfsense forums how often the pfsense firewall actually updates these SNMP counters. Cacti is only seeing what's actually reported.

[DutchSamurai]

I figured this out. Setting the poller to anything other than the cron interval seems to cause this problem. With everything set to one minute the graph and data volume appears to be correct (minus the peaks not showing).

[DutchSamurai]

Or I thought. Cacti broke down on its own and even after a reinstall traffic reporting is inaccurate as hell. On every 100MB it will add about 10MB. The problem isn't with what's being reported from the firewall.

Is there anyway to get Cacti to work as it should?

[wenko]

One thing worth considering is that you are likely graphing averages, not peaks. My pfSense FW is graphed by Cacti and mine is based on averages over the polling interval. I am not sure there is an OID for peak as it would need some significant logic behind it. Your other option is to write a perl script to query it more frequently (as frequently as it allows, say 5s) then sort that data in an array and take the largest value, the peak, and use that as your data point instead of an average (Sum divided by number of samples).