3 Replies Latest reply on Dec 22, 2008 5:02 PM by Andy McBride

    Netflow - discarded traffic

      Is there a good way to know what netflow traffic is being discarded by NTA because its coming from an unmanged interface?

      We can do network capture but decyphering the data willt take forever.... considering we have close to a hundered devices sending netflow.



        • Re: Netflow - discarded traffic


          I'm not sure if this method is any less tedious than taking a packet capture, but you can try to decypher the traffic using the "show ip cache flow" command.  This will give you a list of traffic from source interfaces and source IP addresses with the destination interface, ip address and port the traffic is being sent to.  The fun part is the well known port number is listed in hexadecimal format.  The following is the list of field descriptions from the NetFlow Command Reference guide from Cisco.

          Table 16show ip cache flow Field Descriptions in NetFlow Record Display
          Field                                              Description
          SrcIf                                              Interface on which the packet was received.
          SrcIPaddress                                IP address of the device that transmitted the packet.
          DstIf                                             Interface from which the packet was transmitted.
                                                               Note: If an asterisk (*) immediately follows the DstIf field, the flow being shown is an egress flow.
          DstIPaddress                                IP address of the destination device.
          Pr                                                  IP protocol “well-known” port number, displayed in hexadecimal format. (Refer to http://www.iana.org, Protocol Assignment                                                                      Number Services, for the latest RFC values.)
          SrcP                                              The source protocol port number in hexadecimal.
          DstP                                              The destination protocol port number in hexadecimal.
          Pkts                                              Number of packets switched through this flow.

          Hope this helps.