Collecting Proprietary Flow Fields

nProbe is not only able to collect standard flow fields, that is, those defined in the NetFlow/IPFIX RFCs, it is also able to collect custom and proprietary flow fields. Proprietary fields are ofen used by vendors to export data using standard NetFlow v9 or IPFIX for the transport. Cisco Application Visibility and Control (AVC), Cisco Medianet, IXIA IxFlow, and SonicWall AppFlow are just a few examples.

Proprietary fields can be declared using a plain text file that has to be input to nProbe and they will be treated by nProbe as if they were regular, standard fields. This means that those fields can be exported simply by specifying them in the template -T.

The plain text file has one or more lines in the following format:

Name          STANDARD_ALIAS  PEN     FieldId         Len     Format
  • Name is just a mnemonic name assigned to the proprietary field that is used to identify the field within nProbe, for example when indicating the field in the template.
  • STANDARD_ALIAS is a mapping to a standard field. NONE can be specified when no mapping to a standard field is available. Typically, it is useful to specify this mapping to convert proprietary fields into standard, well-known ones.
  • PEN is the Private Enterprise Number of the proprietary field. If the field has no PEN it is safe to specify 0.
  • FieldId is the integer number that, along with the PEN, uniquely identifies the proprietary field.
  • Len is the length of the field, expressed in bytes.
  • Format specifies how to interpret the bytes of the field:
    • dump_as_uint interprets the field as an unsigned integer
    • dump_as_ipv4_address interprets the field as an IPv4 address
    • dump_as_mac_address interprets the field as a mac address
    • dump_as_hex interprets the field as an hexadecimal value
    • dump_as_ascii as a text string in ASCII format.

Available Custom Flow Fields Definitions

nProbe comes with preconfigured vendor flow definitions, so users can immediately collect popular flow fields without having to create a custom flow configuration. The list of available configurations is available at


A snippet of a text file with the declaration of custom fields for a few vendors is available below:

# Name                STANDARD_ALIAS  PEN     FieldId         Len     Format
# Notes
#   If this field is equivalenet/alias of a standard field, put its name here
#   or put NONE if there is no standard equivalent element
# Notes
# - Use 0 for no PEN
# Available formats
# - dump_as_uint
# - dump_as_ipv4_address
# - dump_as_mac_address
# - dump_as_hex
# - dump_as_ascii

# Gigamon
HttpReqUrl                    NONE    26866   1       64      dump_as_ascii
DnsQueryName                  NONE    26866   204     64      dump_as_ascii
DnsResponseIpv4Address        NONE    26866   207     4       dump_as_ipv4_address

Let’s assume proprietary fields HttpReqUrl and DnsQueryName have to be exported. one can put the declarations in a text file custom-fields.txt and start nProbe as

./nprobe --load-custom-fields "custom-fields.txt" -T  "@NTOPNG@ %HttpReqUrl %DnsQueryName" ...


This is an nProbe Professional feature only.