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  • Troubleshooting opFlow

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Code Block
/usr/local/opmantek/bin/opflow_purge_raw_files.sh /var/opflow 7
/usr/local/opmantek/bin/opflowd.pl type=purge

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Are NetFlow packets arriving at the server?

You have verified that flowd/nfcapd and opflowd are running, but still you have no data on your dashboard. There are several things to check:

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Code Block
/usr/local/omk/bin/nfdump -o raw -r nfcapd.201606090829
# prints every flow record in that file, followed by a short statistics section:
Summary: total flows: 1562, total bytes: 1858493, total packets: 7904, avg bps: 7556, avg pps: 4, avg bpp: 235
Time window: 2016-06-09 08:28:23 - 2016-06-09 09:01:10
Total flows processed: 1562, Blocks skipped: 0, Bytes read: 131400
Sys: 0.052s flows/second: 29477.3    Wall: 0.219s flows/second: 7113.2    

Verify Flow Data is Received

using tcpdump we can verify that flow data is being received by the server.  This example uses the default opFlow UDP port of 9995.  Specify the specific host that needs to be verified.

Code Block
[root@poller001 nfdump]# tcpdump -nn -i eth2 host 10.10.1.1 and port 9995
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth2, link-type EN10MB (Ethernet), capture size 65535 bytes

13:24:55.767037 IP 10.10.1.1.62757 > 10.215.1.7.9995: UDP, length 168
13:25:07.827152 IP 10.10.1.1.62757 > 10.215.1.7.9995: UDP, length 168

When we see output such as the example above we know this server is receiving flow data from the network device.

Check the Flow Data

The next step is to ensure the host in question is providing valid data that nfdump can process.  Move to the /var/lib/nfdump directory and look for nfcapd files that end in a datestamp.  The datestamp denotes the time the capture file was started.  Select a file that is likely to contain samples from the host we with to verify and execute the following command.

Code Block
[root@poller001 nfdump]# nfdump -r nfcapd.201707111327 -o raw > ~/raw.txt

Now view the new text file with less or a text editor.  It will provide flow records such as the following.  The 'ip router' field denotes the source router for this flow sample.

Code Block
Flow Record: 
  Flags        =              0x00 FLOW, Unsampled
  export sysid =                 1
  size         =                76
  first        =        1499779596 [2017-07-11 22:26:36]
  last         =        1499779596 [2017-07-11 22:26:36]
  msec_first   =               447
  msec_last    =               447
  src addr     =         10.10.1.4
  dst addr     =         10.10.1.1
  src port     =             23232
  dst port     =               179
  fwd status   =                 0
  tcp flags    =              0x02 ....S.
  proto        =                 6 TCP  
  (src)tos     =               192
  (in)packets  =                 1
  (in)bytes    =                44
  input        =                 4
  output       =                 0
  src as       =                 0
  dst as       =                 0
  src mask     =                32 10.10.1.4/32
  dst mask     =                32 10.10.1.1/32
  dst tos      =                 0
  direction    =                 0
  ip next hop  =           0.0.0.0
  ip router    =         10.10.1.1
  engine type  =                 0
  engine ID    =                 0
  received at  =     1499747221750 [2017-07-11 13:27:01.750]

Look for things are are not correct in the flow record.  The following issues have been found in past support cases.

  • input/output:  These fields should be the SNMP index number of the input or output interfaces.
  • first/last:  This is a timestamp that the router assigns.  It's important that the router time is in sync with opFlow time.  opFlow uses this time to calculate statistics.  For example, if the router time is an hour earlier than the server time, opFlow will not display the data until the server time catches up with the router time.

Are netflow packets sent where they are expected?

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In the example above you can see for what interfaces and when agents have supplied data. The cli tool also lets you disable agents or particular agent-input-output combinations.

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Ignoring flow sources

When configurations are copied from one device to another flow configuration can come with them, this can lead to more flows being sent to opFlow than is expected.  The best solution to this problem is to stop the device from sending flows, but this cannot always be done (or done in a timely manner).

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with the desired agent ip address and in and out interface indices. If you omit the in_if and out_if arguments, all flow data from this agent is ignored; otherwise only flows that  pass the specifed interfaces in the given direction are filtered out. Please note that deactivating an agent does not affect flows that have already been processed; only future inputs are filtered.

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opFlow and opFlowSP are both set under opCommon.nmis 'omkd' =>  'load_applications'

Either opFlow or opFlowSP should be set, not both.
Otherwise, for example, opFlow uses the incorrect database in mongodb, 'flowsp' rather than 'flows'.
When making a change to this setting from opFlow to opFlowSP, and vice versa, restart the opflowd and omkd services:

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