I'm trying to use nfcapd to capture data from a Cisco router, and it is
only generating empty 276 byte files in the flow directory. I'm using
OSSIM, with the latest version of nfcapd (1.6.3) downloaded from the
Sourceforge site and compiled from source.

The router is configured properly - I've been harvesting flows from it
with the FlowViewer toolset for a long time.

ip flow-export source FastEthernet0/0
ip flow-export version 5
ip flow-export destination [ossim server IP] 9997

Nfcapd is listening to the proper port.

# ps ax | grep nfcap

 3418 ?        S<     0:00 /usr/bin/nfcapd -w -D -I router -p 9997 -u
www-data -g www-data -B 200000 -S 7 -l
/var/cache/nfdump/flows/live/router -P /var/nfsen/run/router.pid

# lsof -i:9997
COMMAND  PID     USER   FD   TYPE DEVICE SIZE NODE NAME
nfcapd  3418 www-data    4u  IPv4 220197       UDP *:9997

Tcpdump shows the traffic coming in.

# tcpdump udp port 9997
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
09:15:18.183766 IP [router].51912 > [ossim server].9997: UDP, length 1464
09:15:22.190789 IP [router].51912 > [ossim server].9997: UDP, length 1464

For some reason, even though the traffic is coming in to the port that
nfcapd is listening to, it's just not recognizing it as Netflow traffic.
I've restarted the daemon, restarted the machine, changed ports, removed
and reconfigured the flow-export rules on the router; nothing seems to
make nfcapd recognize this traffic properly.

Does anyone have any ideas for other things I could try? I don't know
where else to look for possible solutions.

-- 
Matt Gracie                         (716) 888-8378
Information Security Administrator  [email protected]
Canisius College ITS                Buffalo, NY
http://www2.canisius.edu/~graciem/graciem_public_key.gpg        

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