I have installed the Paessler PRTG Network Monitor Freeware version, to monitor internet bandwitdth usage for a Cisco 1811 router.
Configured on the probe are two sensors, each monitoring the 1811 wan interface fa0.
1. Sensor #1 - FlowNet v9 sensor, configured for all available channels and 'detail'.
2. Sensor #2 - SNMP traffic sensor, configured for total traffic.
I am trying to compare the two sensors. I would think that the total traffic volume on the two sensors for the same time period should be the same. But I am seeing almost 4x more traffic on the SNMP sensor than the NetFlow v9 sensor.
Can someone shed some light on what may account for this disparity? And, or, indicate where I may have made errors in my configuration?
The 1811 IOS 12.4(22)T5 has the following relevant configuration.
ip flow ingress
ip flow egress
ip flow-cache timeout inactive 10
ip flow-cache timeout active 5
ip flow-export version 9
ip flow-export destination 192.168.1.10 9991
snmp-server community public RO
Thanks for any assistance.