Traffic graph accuracy

[Wildmike556]

I have been suspecting some problems with my graphs monitoring ethernet uplink ports for some time. There are graphs where an entire building is connected to a single gigabit uplink where the graph doesn't show the bandwidth ever passing 4Mbits or so, but I'm sure that the traffic must be surpassing that frequently, as friends of mine in the buildings I'm monitoring say they routinely use more than that.

I have the maximum value for the data source set to 18446744073709551616 (the highest number you can get with a 64-bit counter), but it doesn't make any difference.

Any suggestions?

[BelgianViking]

Make sure you're not putting MBytes/second values in your graph ! Do an SNMP-get on the value and compare it to the graph.

[Wildmike556]

The graphs that I'm creating are indeed in Mbytes, but still, I'm sure there's more going through these links than that. The ports I'm monitoring are gigabit fiber uplinks, each serving several college residence halls. Especially during evening hours I find it unlikely that the average for any of these ports would be as low as 4Mbytes per second, sustained. I know people that will often transfer several gigabytes into or off of campus, and I never see a spike.

I'm running version 0.8.5a on this particular machine - could there be some sort of math problem in the default graphs that's causing this?

[ssams]

what model switch?

sometimes to verify i use solarwinds bandwidth gauge or performance monitor to validate my findings.

you can also look at the interface on the switch if it is ios based and look at 5min average.

i cant remember which one it was but i did have an ios that had a bug in the counters. that was a few years ago.

[TheWitness]

If it's a device that typically reindexes, you need to upgrade to 0.8.6c. This happens with routers more often than switches. Of course you know that snmpv2 is required.

Regards,

TheWitness

[Wildmike556]

I've been monitoring using SNMPv1 because I don't know for sure what version the switches have on them.

For the most part I'm monitoring Nortel switches, models BPS 2000, BayStack 450 and BayStack 470.

Was SNMPv2 required for monitoring routers that reindex or just traffic monitoring period?

[TheWitness]

snmpv2 is required for interfaces over 100mbps when you are using a 32bit counter. Gigabit interfaces are ~1.2Gbps. Therefore, they require a 64bit counter that is only provided when using snmpv2 or snmpv3.

TheWitness