2
6 flow-tools — Tool set for working with NetFlow data.
7
9 Flow-tools is library and a collection of programs used to collect,
10 send, process, and generate reports from NetFlow data. The tools can
11 be used together on a single server or distributed to multiple servers
12 for large deployments. The flow-toools library provides an API for
13 development of custom applications for NetFlow export versions 1,5,6
14 and the 14 currently defined version 8 subversions. A Perl and Python
15 interface have been contributed and are included in the distribution.
16 Flow data is collected and stored by default in host byte order, yet
18 the files are portable across big and little endian architectures.
19 Commands that utilize the network use a localip/remoteip/port designa‐
21 tion for communication. "localip" is the IP address the host will use
22 as a source for sending or bind to when receiving NetFlow PDU's (ie the
23 destination address of the exporter. Configuring the "localip" to 0
24 will force the kernel to decide what IP address to use for sending and
25 listen on all IP addresses for receiving. "remoteip" is the destina‐
26 tion IP address used for sending or the expected address of the source
27 when receiving. If the "remoteip" is 0 then the application will
28 accept flows from any source address. The "port" is the UDP port num‐
29 ber used for sending or receiving. When using multicast addresses the
30 localip/remoteip/port is used to represent the source, group, and port
31 respectively.
32 Flows are exported from a router in a number of different configurable
34 versions. A flow is a collection of key fields and additional data.
35 The flow key is {srcaddr, dstaddr, input, output, srcport, dstport,
36 prot, ToS}. Flow-tools supports one export version per file.
37 Export versions 1, 5, 6, and 7 all maintain {nexthop, dPkts, dOctets,
39 First, Last, flags}, ie the next-hop IP address, number of packets,
40 number of octets (bytes), start time, end time, and flags such as the
41 TCP header bits. Version 5 adds the additional fields {src_as, dst_as,
42 src_mask, dst_mask}, ie source AS, destination AS, source network mask,
43 and destination network mask. Version 7 which is specific to the Cata‐
44 lyst switches adds in addition to the version 5 fields {router_sc},
45 which is the Router IP address which populates the flow cache shortcut
46 in the Supervisor. Version 6 which is not officially supported by
47 Cisco adds in addition to the version 5 fields {in_encaps, out_encaps,
48 peer_nexthop}, ie the input and output interface encapsulation size,
49 and the IP address of the next hop within the peer. Version 1 exports
50 do not contain a sequence number and therefore should be avoided,
51 although it is safe to store the data as version 1 if the additional
52 fields are not used.
53 Version 8 IOS NetFlow is a second level flow cache that reduces the
55 data exported from the router. There are currently 11 formats, all of
56 which provide {dFlows, dOctets, dPkts, First, Last} for the key fields.
57 8.1 - Source and Destination AS, Input and Output interface
59 8.2 - Protocol and Port
60 8.3 - Source Prefix and Input interface
61 8.4 - Destination Prefix and Output interface
62 8.5 - Source/Destination Prefix and Input/Output interface
63 8.9 - 8.1 + ToS
64 8.10 - 8.2 + ToS
65 8.11 - 8.3 + ToS
66 8.12 - 8.5 + ToS
67 8.13 - 8.2 + ToS
68 8.14 - 8.3 + ports + ToS
69 Version 8 CatIOS NetFlow appears to be a less fine grained first level
71 flow cache.
72 8.6 - Destination IP, ToS, Marked ToS,
74 8.7 - Source/Destination IP, Input/Output interface, ToS, Marked ToS,
75 8.8 - Source/Destination IP, Source/Destination Port,
76 Input/Output interface, ToS, Marked ToS,
77 The following programs are included in the flow-tools distribution.
79 flow-capture - Collect, compress, store, and manage disk space for
81 exported flows from a router.
82 flow-cat - Concatenate flow files. Typically flow files will contain a
84 small window of 5 or 15 minutes of exports. Flow-cat can be used to
85 append files for generating reports that span longer time periods.
86 flow-fanout - Replicate NetFlow datagrams to unicast or multicast des‐
88 tinations. Flow-fanout is used to facilitate multiple collectors
89 attached to a single router.
90 flow-report - Generate reports for NetFlow data sets. Reports include
92 source/destination IP pairs, source/destination AS, and top talkers.
93 Over 50 reports are currently supported.
94 flow-tag - Tag flows based on IP address or AS #. Flow-tag is used to
96 group flows by customer network. The tags can later be used with flow-
97 fanout or flow-report to generate customer based traffic reports.
98 flow-filter - Filter flows based on any of the export fields. Flow-
100 filter is used in-line with other programs to generate reports based on
101 flows matching filter expressions.
102 flow-import - Import data from ASCII or cflowd format.
104 flow-export - Export data to ASCII or cflowd format.
106 flow-send - Send data over the network using the NetFlow protocol.
108 flow-receive - Receive exports using the NetFlow protocol without stor‐
110 ing to disk like flow-capture.
111 flow-gen - Generate test data.
113 flow-dscan - Simple tool for detecting some types of network scanning
115 and Denial of Service attacks.
116 flow-merge - Merge flow files in chronoligical order.
118 flow-xlate - Perform translations on some flow fields.
120 flow-expire - Expire flows using the same policy of flow-capture.
122 flow-header - Display meta information in flow file.
124 flow-split - Split flow files into smaller files based on size, time,
126 or tags.
127
129 Mark Fullmer maf@splintered.net
130 flow-merge by Larry Lidz ellidz@eridu.uchicago.edu
132 Patches and other contribitions by a list too long to mention here.
134 flow-tools is avalable at
136 (link to URL http://www.splintered.net/sw/flow-tools) .
137 A mailing list is maintained at flow-tools@splintered.net
139
141 flow-capture(1) flow-cat(1) flow-dscan(1) flow-expire(1) flow-export(1)
142 flow-fanout(1) flow-filter(1) flow-nfilter(1) flow-gen(1) flow-
143 header(1) flow-import(1) flow-merge(1) flow-print(1) flow-receive(1)
144 flow-report(1) flow-send(1) flow-split(1) flow-stat(1) flow-tag(1)
145 flow-xlate(1)
146 flow-tools(1)