I have/had a NetFlow v9 sensor setup to capture data from a customers Cisco router.
This was working but I needed to use it for an investigation last week and it was reporting no data received since September, I can still see historic data on the 365 day chart. No one is aware of any changes made to either Cisco or PRTG at this time but, frankly, it was a while ago and we can't be 100% sure.
I have attempted to resolve ths issue by doing the following.
1. verify the netflow data is being generated by Cisco.
Cisco was configured to export flow data on UDP port 12245. For testing purposes I have added a second exporter on UDP port 9996
ip flow-export source Vlan82 ip flow-export version 9 ip flow-export destination 192.168.50.2 9996 ip flow-export destination 192.168.50.2 12245 ip flow-top-talkers top 20 sort-by bytes cache-timeout 360 match destination address 0.0.0.0 0.0.0.0 !
With the PRTG service stopped (to free up the ports) both the free ManageEngine OP Netflow sensor and your own Paessler NetFlow tool show data being received on both ports. The ManageEngine sensor is correctly identifying top talkers and other flow data.
2. Check the remote probe
I have verified that the PRTG probe is listening on the UDP ports specified with "NETSTAT -a -n -o" which correctly displays the listening port associated with the PRTG process ID. These listening ports appear and disappear when I stop or start the probe service.
I have verified the configuration from the PRTG interface. I've created a duplicate Netflow sensor, so I have now one running on 12245 and one on 9996. Neither of these ports are showing data when I stop the PRTG sensor and start the ManageEngine one I have made sure that there are no port conflicts on the receiving probe server. I've uninstalled and resintalled the sensor
3. Test remote probe
Using the Paessler Netflow Generator I am generating test data to either/both ports, neither are showing any data on the PRTG interface (both are showing 'No data received since...').