Provided by: nfdump_1.6.23-1_amd64 
NAME
nfcapd - netflow capture daemon
SYNOPSIS
nfcapd [options]
DESCRIPTION
nfcapd is the netflow capture daemon of the nfdump tools. It reads netflow data from the network and
stores it into files. The output file is automatically rotated and renamed every n minutes - typically 5
min - according the timestamp YYYYMMddhhmm of the interval e.g. nfcapd.201907110845 contains the data
from July 11th 2019 08:45 onward. If the time interval is smaller then 60s, the naming extends to
seconds e.g. nfcapd.20190711084510.
Netflow version v1, v5, v7 and v9 and IPFIX are transparently supported.
Extensions: nfcapd supports a large number of v9 tags. In order to optimise disk space and performance,
v9 tags are grouped into a number of extensions which may or may not be stored into the data file.
Therefore the v9 templates configured on the exporter may be tuned according the collector. Only those
tags common to both are stored into the data files.
Sampling: By default, the sampling rate is set to 1 (unsampled) or to any given value specified by the -s
cmd line option. If sampling information is found in the netflow stream, it overwrites the default value.
Sampling is automatically recognised when announced in v9 option templates (tags #34, #35 or #48, #49,
#50 ) or in the unofficial v5 header hack. Note: Not all platforms (or IOS/JunOS versions) support
exporting sampling information in netflow data, even if sampling is configured. The number of
bytes/packets in each netflow record is automatically multiplied by the sampling rate. The total number
of flows is not changed as this is not accurate enough. (Small flows versus large flows) If the default
sampling rate given by -s is negative, this will hard overwrite any device specific announced sampling
rates.
NSEL/ASA Support: nfcapd can be compiled with NSEL/ASA support included. See notes on NSEL/ASA
NEL (NAT Event logging): nfcapd can be compiled with CISCO NEL support included. See notes on NEL.
OPTIONS
-p portnum
Specifies the port number to listen. Default port is 9995
-b bindhost
Specifies the hostname/IPv4/IPv6 address to bind for listening. This can be an IP address or a
hostname, resolving to an IP address attached to an interface. Defaults to any available IPv4
interface, if not specified.
-4 Forces nfcapd to listen on IPv4 addresses only. Can be used together with -b if a hostname has an IPv4
and IPv6 address record.
-6 Forces nfcapd to listen on IPv6 addresses only. Can be used together with -b if a hostname has an IPv4
and IPv6 address record. Depending on the socket implementation -6 also accepts IPv4 data.
-J MulticastGroup
Join the specified IPv4 or IPv6 multicast group for listening.
-R host[/port}
Enable packet repeater. Send all incoming packets to another host and port. host is either a valid
IPv4/IPv6 address, or a valid symbolic hostname, which resolves to a IPv6 or IPv4 address. port may be
omitted and defaults to port 9995. Note: Due to IPv4/IPv6 accepted addresses the port separator is
'/'. Up to 8 repeaters my be defined.
-I IdentString ( capital letter i )
Specifies an ident string, which describes the source e.g. the name of the router. This string is put
into the stat record to identify the source. Default is 'none'. This is for compatibility with nfdump
1.5.x and used to specify a single netflow source. See -n
-l base_directory ( letter ell )
Specifies the base directory to store the output files. If a sub hierarchy is specified with -S the
final directory is concatenated to base_directory/sub_hierarchy. This is for compatibility with nfdump
1.5.x and used to specify a single netflow source. See -n
-n <Ident,IP,base_directory>
Configures a netflow source named Ident and identified by source IP address IP. The base directory
for the flow files is base_directory. If a sub hierarchy is specified with -S the final directory is
concatenated to base_directory/sub_hierarchy. Multiple netflow sources can be specified. All data is
sent to the same port specified by -p. Note: You must not mix -n option with -I and -l. Use either
syntax.
-N <file>
Specifies the file to read to add multiple netflow sources. The file is expected to contain one
netflow source per line based on the same syntax than the -n option. Comments are not interpreted.
Ident collision are not handled if -N is specified multiple times.
-M <dynbase_directory>
Specifies the base directory to store the output files. In contrast to -l -M allows to add dynamically
new flow sources (exporters), as they appear. All exporters send netflow data to the same port and IP.
For each dynamically added source, a new directory is created with the name of the IPv4/IPv6 address
of the exporter. All '.' and ':" in IP addresses are replaced be '-' e.g. 10.11.12.13 is converted to
the directory name 10-11-12-13. Note: Please make sure to restrict at host level the potential range
of IP addresses which are allowed to connect to nfcapd. Otherwise you risk a potential DoS attack on
nfcapd, as nfcapd has no built in restrictions.
-f <pcap_file>
Read netflow packets from a give pcap_file instead of the network. This requires nfcapd to be compiled
with the pcap option and is intended for debugging only.
-s <rate>
Apply default sampling rate rate to all netflow records, unless the sampling rate is announced by the
exporting device. In that case the announced sampling rate is applied. If <rate> is negative, this
will hard overwrite any device specific announced sampling rates.
-S <num>
Allows to specify an additional directory sub hierarchy to store the data files. The default is 0, no
sub hierarchy, which means the files go directly in the base directory (-l). The base directory (-l)
is concatenated with the specified sub hierarchy format to form the final data directory. The
following hierarchies are defined:
0 default no hierarchy levels
1 %Y/%m/%d year/month/day
2 %Y/%m/%d/%H year/month/day/hour
3 %Y/%W/%u year/week_of_year/day_of_week
4 %Y/%W/%u/%H year/week_of_year/day_of_week/hour
5 %Y/%j year/day-of-year
6 %Y/%j/%H year/day-of-year/hour
7 %Y-%m-%d year-month-day
8 %Y-%m-%d/%H year-month-day/hour
-T <extension list>
The argument is considered legacy. By default all matching extension sent by the exporter are stored.
You still may overwrite this, if you want to skip certain extansions. Regardless of the extension
list, the following netflow data is stored per record: first, last, fwd status, tcp flags, proto,
(src)tos, src port, dst port, src ipaddr, dst ipaddr, in(packets), in(bytes). In addition nfcapd
recognises the extensions as described below. Some are valid for v5/v7/v9, but most of them make only
sense for v9. Any specified extensions which do not exist in the input netflow records are ignored.
Extensions:
v5/v7/v9/IPFIX extensions:
1 input/output interface SNMP numbers.
2 src/dst AS numbers.
3 src/dst mask, (dst)TOS, direction.
4 line Next hop IP addr line
5 line BGP next hop IP addr line
6 src/dst vlan id labels
7 counter output packets
8 counter output bytes
9 counter aggregated flows
10 in_src/out_dst MAC address
11 in_dst/out_src MAC address
12 MPLS labels 1-10
13 Exporting router IPv4/IPv6 address
14 Exporting router ID
15 BGP adjacent prev/next AS
16 time stamp flow received by the collector
NSEL/ASA/NAT extensions
26 NSEL ASA event, xtended event, ICMP type/code
27 NSEL/NAT xlate ports
28 NSEL/NAT xlate IPv4/IPv6 addr
29 NSEL ASA ACL ingress/egress acl ID
30 NSEL ASA username
NEL/NAT extensions
31 NAT event, ingress egress vrfid
32 NAT Block port allocation - block start, end step and size
latency extension
64 nfpcapd/nprobe client/server/application latency"},
IMPORTANT: By default all extension are selected Extensions can be added/deleted by specifying a ','
separated list of extension ids. Each id may be prepended by an optional sign +/- to add or remove a
given id from the extension list. Shortcuts: The string 'all' means all extensions. The strings
'nsel' and 'nel' enable all NSEL or NEL extensions respectively.
Examples:
-T all Enables all possible extensions.
-T +3,+4 Adds extensions 3 and 4 to the defaults 1 and 2.
-T all,-8,-9 Set all extensions but 8 and 9
-T -1,4 Removes default extension 1 and adds extension 4
-T nsel Enables all required ASA?NSEL extensions
-T nel Enables all required nell extensions
Note: Only those tags in common with the exporting device and enabled extensions at the collector
side are stored into the data files. A detailed list which v9 tags are mapped into which extensions
is given in the section NOTES
-t interval
Specifies the time interval in seconds to rotate files. The default value is 300s ( 5min ). The
smallest interval is 2s.
-w Align file rotation with next n minute ( specified by -t ) interval. Example: If interval is 5 min,
sync at 0,5,10... wall clock minutes Default: no alignment.
-x cmd
Run command cmd at the end of every interval, when a new file becomes available. The following command
expansion is available:
%f Replaced by the file name e.g nfcapd.200907110845 inluding any
sub hierarchy. ( 2009/07/11/nfcapd.200907110845 )
%d Replaced by the directory where the file is located.
%t Replaced by the time ISO format e.g. 200907110845.
%u Replaced by the UNIX time format.
%i Replaced ident string given by -I
-X Collect and embed extended statistics. Currently a port and bpp histogram is embedded. Mostly
experimental for now
-e Auto expire files at every cycle. max lifetime and max filesize are defined using nfexpire(1)
-P pidfile
Specify name of pidfile. Default is no pidfile.
-D Daemon mode: fork to background and detach from terminal. Nfcapd terminates on signal TERM, INT and
HUP.
-u userid
Change to the user userid as soon as possible. Only root is allowed to use this option.
-g groupid
Change to the group groupid as soon as possible. Only root is allowed use this option.
-B bufflen
Specifies the socket input buffer length in bytes. For high volume traffic ( near GB traffic ) it is
recommended to set this value as high as possible ( typically > 100k ), otherwise you risk to lose
packets. The default is OS ( and kernel ) dependent.
-E Print netflow records in nfdump raw format to stdout. This option is for debugging purpose only, to
see how incoming netflow data is processed and stored.
-j Compress flows. Use bz2 compression in output file. Note: not recommended while collecting
-y Compress flows. Use LZ4 compression in output file.
-z Compress flows. Use fast LZO1X-1 compression in output file.
-V Print nfcapd version and exit.
-h Print help text to stdout with all options and exit.
RETURN VALUE
Returns 0 on success, or 255 if initialization failed.
LOGGING
nfcapd logs to syslog with SYSLOG_FACILITY LOG_DAEMON For normal operation level 'warning' should be
fine. More information is reported at level 'info' and 'debug'.
A small statistic about the collected flows, as well as errors are reported at the end of every interval
to syslog with level 'info'.
EXAMPLES
All flows are sent to port 9995 from all exporters and stored into a single file. All known v9 tags are
taken.
nfcapd -z -w -D -T all -l /netflow/spool/allflows -I any -S 2 -P /var/run/nfcapd.allflows.pid
All flows from 2 different exporters are sent to port 8877 and stored in separate directory trees. All
known v9 tags are taken. Input buffer size is set to 128000 bytes
nfcapd -z -w -D -T all -p 8877 -n upstream,192.168.1.1,/netflow/spool/upstream -n
peer,192.168.2.1,/netflow/spool/peer -S 2 -B 128000
Only accept from from a single exporter and only extension 3,4 and 5 are accepted. Run a given command
when files are rotated and automatically expire flows:
nfcapd -w -D -T 3,4,5 -n upstream,192.168.1.1,/netflow/spool/upstream -p 23456 -B 128000 -s 100 -x
'/path/command -r %d/%f' -P /var/run/nfcapd/nfcapd.pid -e
NOTES
Multiple netflow sources:
Netflow data may be sent from different exporters to a single nfcapd process. Use the -n option to
separate each netflow source to a different data directory. For compatibility with nfdump 1.5.x, old
style -l/-I options are still valid. In that case all flows from all sources are stored in a single
file. For high volume netflow streams, it is still recommended to have a single nfcapd process per
netflow source.
Nfdump supports a large number of v9 and ipfix elements. For a detailed list chek the netflow_v9 and
ipfix header files. 32 and 64 bit are supported for all counters. 32it AS numbers are supported.
The format of the data files is netflow version independent.
Socket buffer: Setting the socket buffer size is system dependent. When starting up, nfcapd returns the
number of bytes the buffer was actually set. This is done by reading back the buffer size and may differ
from what you requested.
SEE ALSO
nfdump(1), nfprofile(1), nfreplay(1)
BUGS
No software without bugs! Please report any bugs back to me.
2009-09-09 nfcapd(1)