[nsp] NetFlow not exporting?

Danny McPherson danny at tcb.net
Fri Apr 16 20:07:51 EDT 2004


What version of IOS are you running?  You may be tickling
a flow exportism in more recent versions of IOS,  - be sure
CEF is enabled on the interface.

-danny

On Apr 16, 2004, at 9:31 AM, Chris Moore - GMD wrote:

> Hi all,
>
> I'm experimenting with exporting NetFlow info to nTop. My 3745 seems to
> think it is exporting NetFlow datagrams, but I'm not seeing these 
> packets
> with my sniffer - let alone with nTop. My NetFlow config looks like 
> this:
>
> interface Serial0/0
>  ip address 172.17.1.6 255.255.255.252
>  ip flow ingress
>  ip route-cache flow
>
> ip flow-export version 5
> ip flow-export destination 10.12.23.201 2055
>
> Where 10.12.23.201 is my collector. Very simple - like I said, at this 
> point
> I'm just trying to experiment, "see what I can see".
>
> show ip flow export gives me this:
>
> Flow export v5 is enabled for main cache
>   Exporting flows to 10.12.23.201 (2055)
>   Exporting using source IP address 172.17.1.6
>   Version 5 flow records
>   4657 flows exported in 181 udp datagrams
>   0 flows failed due to lack of export packet
>   0 export packets were sent up to process level
>   0 export packets were dropped due to no fib
>   0 export packets were dropped due to adjacency issues
>   0 export packets were dropped due to fragmentation failures
>   0 export packets were dropped due to encapsulation fixup failures
>
> And show ip flow cache gives me a bunch of info about packet size, 
> protocol
> summaries, conversations, etc - exactly what I would expect to see.
>
> Unfortunately I just don't see the packets on the network. I can 
> generate
> traffic between 172.17.1.6 and 10.12.23.201 using ping or telnet and 
> see
> that just fine on my sniffer, so I'm pretty sure the path is correct, 
> the
> sniffer is in the right place to see the traffic and obviously I'm
> communicationg successfully between the two devices. It looks like the
> router just isn't sending the packets.
>
> My only guess is that it has something to do with the line in the show 
> ip
> flow export output that reads "0 export packets were sent up to process
> level". Unfortunately I have been unable to find an explantation of the
> output in the Cisco docs. But I did find an exaple where the packets 
> sent up
> to process level matched the number of export datagrams. Any help with
> reading the output of that command?
>
> Any ideas what's happening to the NetFlow UDP packets?
>
> Thanks,
>
> Chris
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