I have been receiving the following msg in PRTG (using v8.4.2.2381) : The netflow sensor has received and dropped flows with a timestamp older than the timespan defined by the active flow timeout.

I recently have added netflow to all our routers (40). Since then i have been getting the above message. But not often, once or twice a day, sometimes nothing. So im figuring this is a problem with only one of the devices. I wonder why the message cant specify which netflow sensor is causing this problem, cause searching on all routers is not really that great. I however have checked every router and all settings. After that i checked all the settings within PRTG. Everything is exacly the same on all devices, yet i still receive this error now and again.

Is there any way to track this ? what sensor is sending me this message ?

Article Comments

hallo,

what is the active flow timeout set to on your routers and in the netflow sensors?

are you sending all flows to the same port on your PRTG server?


Oct, 2011 - Permalink

This is the config as how i put them in my routers :

configure terminal
interface FastEthernet 0/1
ip route-cache flow
exit 
ip flow-export destination 172.17.7.70 2052
ip flow-export source FastEthernet 0/1
ip flow-export version 9
ip flow-cache timeout active 1
ip flow-cache timeout inactive 15
snmp-server ifindex persist
exit
wr

I use a different port for each router.


Oct, 2011 - Permalink

hallo,

and what is the active flow timeout in the sensors set to?

It should be 1min more than the setting on the device.


Oct, 2011 - Permalink

That is correct, they are all set to 2.


Oct, 2011 - Permalink