9 iftop - display bandwidth usage on an interface by host
12 S
\bSY
\bYN
\bNO
\bOP
\bPS
\bSI
\bIS
\bS
13 i
\bif
\bft
\bto
\bop
\bp -
\b-h
\bh | [-
\b-n
\bnN
\bNp
\bpb
\bbl
\blB
\bBP
\bP] [-
\b-i
\bi _
\bi_
\bn_
\bt_
\be_
\br_
\bf_
\ba_
\bc_
\be] [-
\b-f
\bf _
\bf_
\bi_
\bl_
\bt_
\be_
\br _
\bc_
\bo_
\bd_
\be] [-
\b-F
\bF _
\bn_
\be_
\bt/_
\bm_
\ba_
\bs_
\bk] [-
\b-G
\bG
14 _
\bn_
\be_
\bt_
\b6/_
\bm_
\ba_
\bs_
\bk_
\b6]
16 D
\bDE
\bES
\bSC
\bCR
\bRI
\bIP
\bPT
\bTI
\bIO
\bON
\bN
17 i
\bif
\bft
\bto
\bop
\bp listens to network traffic on a named _
\bi_
\bn_
\bt_
\be_
\br_
\bf_
\ba_
\bc_
\be, or on the first
18 interface it can find which looks like an external interface if none is
19 specified, and displays a table of current bandwidth usage by pairs of
20 hosts. i
\bif
\bft
\bto
\bop
\bp must be run with sufficient permissions to monitor all
21 network traffic on the _
\bi_
\bn_
\bt_
\be_
\br_
\bf_
\ba_
\bc_
\be; see p
\bpc
\bca
\bap
\bp(3) for more information, but
22 on most systems this means that it must be run as root.
24 By default, i
\bif
\bft
\bto
\bop
\bp will look up the hostnames associated with addresses
25 it finds in packets. This can cause substantial traffic of itself, and
26 may result in a confusing display. You may wish to suppress display of
27 DNS traffic by using filter code such as n
\bno
\bot
\bt p
\bpo
\bor
\brt
\bt d
\bdo
\bom
\bma
\bai
\bin
\bn, or switch it
28 off entirely, by using the -
\b-n
\bn option or by pressing r
\br when the program
31 By default, i
\bif
\bft
\bto
\bop
\bp counts all IP packets that pass through the filter,
32 and the direction of the packet is determined according to the direc-
33 tion the packet is moving across the interface. Using the -
\b-F
\bF option it
34 is possible to get i
\bif
\bft
\bto
\bop
\bp to show packets entering and leaving a given
35 network. For example, i
\bif
\bft
\bto
\bop
\bp -
\b-F
\bF 1
\b10
\b0.
\b.0
\b0.
\b.0
\b0.
\b.0
\b0/
\b/2
\b25
\b55
\b5.
\b.0
\b0.
\b.0
\b0.
\b.0
\b0 will analyse packets
36 flowing in and out of the 10.* network.
38 Some other filter ideas:
40 n
\bno
\bot
\bt e
\bet
\bth
\bhe
\ber
\br h
\bho
\bos
\bst
\bt f
\bff
\bf:
\b:f
\bff
\bf:
\b:f
\bff
\bf:
\b:f
\bff
\bf:
\b:f
\bff
\bf:
\b:f
\bff
\bf
41 Ignore ethernet broadcast packets.
43 p
\bpo
\bor
\brt
\bt h
\bht
\btt
\btp
\bp a
\ban
\bnd
\bd n
\bno
\bot
\bt h
\bho
\bos
\bst
\bt _
\bw_
\be_
\bb_
\bc_
\ba_
\bc_
\bh_
\be_
\b._
\be_
\bx_
\ba_
\bm_
\bp_
\bl_
\be_
\b._
\bc_
\bo_
\bm
44 Count web traffic only, unless it is being directed through a
47 i
\bic
\bcm
\bmp
\bp How much bandwidth are users wasting trying to figure out why
51 O
\bOP
\bPT
\bTI
\bIO
\bON
\bNS
\bS
52 -
\b-h
\bh Print a summary of usage.
54 -
\b-n
\bn Don't do hostname lookups.
56 -
\b-N
\bN Do not resolve port number to service names
58 -
\b-p
\bp Run in promiscuous mode, so that traffic which does not pass
59 directly through the specified interface is also counted.
61 -
\b-P
\bP Turn on port display.
63 -
\b-l
\bl Display and count datagrams addressed to or from link-local IPv6
64 addresses. The default is not to display that address category.
66 -
\b-b
\bb Don't display bar graphs of traffic.
68 -
\b-m
\bm _
\bl_
\bi_
\bm_
\bi_
\bt
69 Set the upper limit for the bandwidth scale. Specified as a
70 number with a 'K', 'M' or 'G' suffix.
72 -
\b-B
\bB Display bandwidth rates in bytes/sec rather than bits/sec.
74 -
\b-i
\bi _
\bi_
\bn_
\bt_
\be_
\br_
\bf_
\ba_
\bc_
\be
75 Listen to packets on _
\bi_
\bn_
\bt_
\be_
\br_
\bf_
\ba_
\bc_
\be.
77 -
\b-f
\bf _
\bf_
\bi_
\bl_
\bt_
\be_
\br _
\bc_
\bo_
\bd_
\be
78 Use _
\bf_
\bi_
\bl_
\bt_
\be_
\br _
\bc_
\bo_
\bd_
\be to select the packets to count. Only IP packets
79 are ever counted, so the specified code is evaluated as (
\b(_
\bf_
\bi_
\bl_
\bt_
\be_
\br
80 _
\bc_
\bo_
\bd_
\be)
\b) a
\ban
\bnd
\bd i
\bip
\bp.
82 -
\b-F
\bF _
\bn_
\be_
\bt/_
\bm_
\ba_
\bs_
\bk
83 Specifies an IPv4 network for traffic analysis. If specified,
84 iftop will only include packets flowing in to or out of the
85 given network, and packet direction is determined relative to
86 the network boundary, rather than to the interface. You may
87 specify _
\bm_
\ba_
\bs_
\bk as a dotted quad, such as /255.255.255.0, or as a
88 single number specifying the number of bits set in the netmask,
91 -
\b-G
\bG _
\bn_
\be_
\bt_
\b6/_
\bm_
\ba_
\bs_
\bk_
\b6
92 Specifies an IPv6 network for traffic analysis. The value of
93 _
\bm_
\ba_
\bs_
\bk_
\b6 can be given as a prefix length or as a numerical address
94 string for more compound bitmasking.
96 -
\b-c
\bc _
\bc_
\bo_
\bn_
\bf_
\bi_
\bg _
\bf_
\bi_
\bl_
\be
97 Specifies an alternate config file. If not specified, iftop
98 will use ~
\b~/
\b/.
\b.i
\bif
\bft
\bto
\bop
\bpr
\brc
\bc if it exists. See below for a description
101 -
\b-t
\bt _
\bt_
\be_
\bx_
\bt _
\bo_
\bu_
\bt_
\bp_
\bu_
\bt _
\bm_
\bo_
\bd_
\be
102 Use text interface without ncurses and print the output to STD-
107 D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY
108 When running, i
\bif
\bft
\bto
\bop
\bp uses the whole screen to display network usage. At
109 the top of the display is a logarithmic scale for the bar graph which
110 gives a visual indication of traffic.
112 The main part of the display lists, for each pair of hosts, the rate at
113 which data has been sent and received over the preceding 2, 10 and 40
114 second intervals. The direction of data flow is indicated by arrows, <=
115 and =>. For instance,
117 foo.example.com => bar.example.com 1Kb 500b 100b
120 shows, on the first line, traffic from f
\bfo
\boo
\bo.
\b.e
\bex
\bxa
\bam
\bmp
\bpl
\ble
\be.
\b.c
\bco
\bom
\bm to b
\bba
\bar
\br.
\b.e
\bex
\bxa
\bam
\bm-
\b-
121 p
\bpl
\ble
\be.
\b.c
\bco
\bom
\bm; in the preceding 2 seconds, this averaged 1Kbit/s, around half
122 that amount over the preceding 10s, and a fifth of that over the whole
123 of the last 40s. During each of those intervals, the data sent in the
124 other direction was about 2Mbit/s. On the actual display, part of each
125 line is inverted to give a visual indication of the 10s average of
126 traffic. You might expect to see something like this where host f
\bfo
\boo
\bo is
127 making repeated HTTP requests to b
\bba
\bar
\br, which is sending data back which
128 saturates a 2Mbit/s link.
130 By default, the pairs of hosts responsible for the most traffic (10
131 second average) are displayed at the top of the list.
133 At the bottom of the display, various totals are shown, including peak
134 traffic over the last 40s, total traffic transferred (after filtering),
135 and total transfer rates averaged over 2s, 10s and 40s.
138 S
\bSO
\bOU
\bUR
\bRC
\bCE
\bE /
\b/ D
\bDE
\bES
\bST
\bT A
\bAG
\bGG
\bGR
\bRE
\bEG
\bGA
\bAT
\bTI
\bIO
\bON
\bN
139 By pressing s
\bs or d
\bd while i
\bif
\bft
\bto
\bop
\bp is running, all traffic for each source
140 or destination will be aggregated together. This is most useful when
141 i
\bif
\bft
\bto
\bop
\bp is run in promiscuous mode, or is run on a gateway machine.
144 P
\bPO
\bOR
\bRT
\bT D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY
145 S
\bS or D
\bD toggle the display of source and destination ports respectively.
146 p
\bp will toggle port display on/off.
149 D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY T
\bTY
\bYP
\bPE
\bE
150 t
\bt cycles through the four line display modes; the default 2-line dis-
151 play, with sent and received traffic on separate lines, and 3 1-line
152 displays, with sent, received, or total traffic shown.
155 D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY O
\bOR
\bRD
\bDE
\bER
\bR
156 By default, the display is ordered according to the 10s average (2nd
157 column). By pressing 1
\b1, 2
\b2 or 3
\b3 it is possible to sort by the 1st, 2nd
158 or 3rd column. By pressing <
\b< or >
\b> the display will be sorted by
159 source or destination hostname respectively.
162 D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY F
\bFI
\bIL
\bLT
\bTE
\bER
\bRI
\bIN
\bNG
\bG
163 l
\bl allows you to enter a POSIX extended regular expression that will be
164 used to filter hostnames shown in the display. This is a good way to
165 quickly limit what is shown on the display. Note that this happens at
166 a much later stage than filter code, and does not affect what is actu-
167 ally captured. Display filters DO NOT affect the totals at the bottom
171 P
\bPA
\bAU
\bUS
\bSE
\bE D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY /
\b/ F
\bFR
\bRE
\bEE
\bEZ
\bZE
\bE O
\bOR
\bRD
\bDE
\bER
\bR
172 P
\bP will pause the current display.
174 o
\bo will freeze the current screen order. This has the side effect that
175 traffic between hosts not shown on the screen at the time will not be
176 shown at all, although it will be included in the totals at the bottom
180 S
\bSC
\bCR
\bRO
\bOL
\bLL
\bL D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY
181 j
\bj and k
\bk will scroll the display of hosts. This feature is most useful
182 when the display order is frozen (see above).
185 F
\bFI
\bIL
\bLT
\bTE
\bER
\bR C
\bCO
\bOD
\bDE
\bE
186 f
\bf allows you to edit the filter code whilst iftop running. This can
187 lead to some unexpected behaviour.
190 C
\bCO
\bON
\bNF
\bFI
\bIG
\bG F
\bFI
\bIL
\bLE
\bE
191 iftop can read its configuration from a config file. If the -
\b-c
\bc option
192 is not specified, iftop will attempt to read its configuration from
193 ~
\b~/
\b/.
\b.i
\bif
\bft
\bto
\bop
\bpr
\brc
\bc, if it exists. Any command line options specified will
194 override settings in the config file.
196 The config file consists of one configuration directive per line. Each
197 directive is a name value pair, for example:
201 sets the network interface. The following config directives are sup-
205 i
\bin
\bnt
\bte
\ber
\brf
\bfa
\bac
\bce
\be:
\b: _
\bi_
\bf
206 Sets the network interface to _
\bi_
\bf.
208 d
\bdn
\bns
\bs-
\b-r
\bre
\bes
\bso
\bol
\blu
\but
\bti
\bio
\bon
\bn:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
209 Controls reverse lookup of IP addresses.
211 p
\bpo
\bor
\brt
\bt-
\b-r
\bre
\bes
\bso
\bol
\blu
\but
\bti
\bio
\bon
\bn:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
212 Controls conversion of port numbers to service names.
214 f
\bfi
\bil
\blt
\bte
\ber
\br-
\b-c
\bco
\bod
\bde
\be:
\b: _
\bb_
\bp_
\bf
215 Sets the filter code to _
\bb_
\bp_
\bf.
217 s
\bsh
\bho
\bow
\bw-
\b-b
\bba
\bar
\brs
\bs:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
218 Controls display of bar graphs.
220 p
\bpr
\bro
\bom
\bmi
\bis
\bsc
\bcu
\buo
\bou
\bus
\bs:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
221 Puts the interface into promiscuous mode.
223 p
\bpo
\bor
\brt
\bt-
\b-d
\bdi
\bis
\bsp
\bpl
\bla
\bay
\by:
\b: _
\b(_
\bo_
\bf_
\bf_
\b|_
\bs_
\bo_
\bu_
\br_
\bc_
\be_
\b-_
\bo_
\bn_
\bl_
\by_
\b|_
\bd_
\be_
\bs_
\bt_
\bi_
\bn_
\ba_
\bt_
\bi_
\bo_
\bn_
\b-_
\bo_
\bn_
\bl_
\by_
\b|_
\bo_
\bn_
\b)
224 Controls display of port numbers.
226 l
\bli
\bin
\bnk
\bk-
\b-l
\blo
\boc
\bca
\bal
\bl:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
227 Determines displaying of link-local IPv6 addresses.
229 h
\bhi
\bid
\bde
\be-
\b-s
\bso
\bou
\bur
\brc
\bce
\be:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
230 Hides source host names.
232 h
\bhi
\bid
\bde
\be-
\b-d
\bde
\bes
\bst
\bti
\bin
\bna
\bat
\bti
\bio
\bon
\bn:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
233 Hides destination host names.
235 u
\bus
\bse
\be-
\b-b
\bby
\byt
\bte
\bes
\bs:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
236 Use bytes for bandwidth display, rather than bits.
238 s
\bso
\bor
\brt
\bt:
\b: _
\b(_
\b2_
\bs_
\b|_
\b1_
\b0_
\bs_
\b|_
\b4_
\b0_
\bs_
\b|_
\bs_
\bo_
\bu_
\br_
\bc_
\be_
\b|_
\bd_
\be_
\bs_
\bt_
\bi_
\bn_
\ba_
\bt_
\bi_
\bo_
\bn_
\b)
239 Sets which column is used to sort the display.
241 l
\bli
\bin
\bne
\be-
\b-d
\bdi
\bis
\bsp
\bpl
\bla
\bay
\by:
\b: _
\b(_
\bt_
\bw_
\bo_
\b-_
\bl_
\bi_
\bn_
\be_
\b|_
\bo_
\bn_
\be_
\b-_
\bl_
\bi_
\bn_
\be_
\b-_
\bb_
\bo_
\bt_
\bh_
\b|_
\bo_
\bn_
\be_
\b-_
\bl_
\bi_
\bn_
\be_
\b-_
\bs_
\be_
\bn_
\bt_
\b|_
\bo_
\bn_
\be_
\b-_
\bl_
\bi_
\bn_
\be_
\b-_
\br_
\be_
\bc_
\be_
\bi_
\bv_
\be_
\bd_
\b)
242 Controls the appearance of each item in the display.
244 s
\bsh
\bho
\bow
\bw-
\b-t
\bto
\bot
\bta
\bal
\bls
\bs:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
245 Shows cumulative total for each item.
247 l
\blo
\bog
\bg-
\b-s
\bsc
\bca
\bal
\ble
\be:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
248 Use a logarithmic scale for bar graphs.
250 m
\bma
\bax
\bx-
\b-b
\bba
\ban
\bnd
\bdw
\bwi
\bid
\bdt
\bth
\bh:
\b: _
\bb_
\bw
251 Fixes the maximum for the bar graph scale to _
\bb_
\bw, e.g. "10M".
252 Note that the value has to always be in bits, regardless if the
253 option to display in bytes has been chosen.
255 n
\bne
\bet
\bt-
\b-f
\bfi
\bil
\blt
\bte
\ber
\br:
\b: _
\bn_
\be_
\bt_
\b/_
\bm_
\ba_
\bs_
\bk
256 Defines an IP network boundary for determining packet direction.
258 n
\bne
\bet
\bt-
\b-f
\bfi
\bil
\blt
\bte
\ber
\br6
\b6:
\b: _
\bn_
\be_
\bt_
\b6_
\b/_
\bm_
\ba_
\bs_
\bk_
\b6
259 Defines an IPv6 network boundary for determining packet direc-
262 s
\bsc
\bcr
\bre
\bee
\ben
\bn-
\b-f
\bfi
\bil
\blt
\bte
\ber
\br:
\b: _
\br_
\be_
\bg_
\be_
\bx_
\bp
263 Sets a regular expression to filter screen output.
266 Q
\bQU
\bUI
\bIR
\bRK
\bKS
\bS (
\b(a
\bak
\bka
\ba t
\bth
\bhe
\bey
\by'
\b'r
\bre
\be f
\bfe
\bea
\bat
\btu
\bur
\bre
\bes
\bs,
\b, n
\bno
\bot
\bt b
\bbu
\bug
\bgs
\bs)
\b)
267 There are some circumstances in which iftop may not do what you expect.
268 In most cases what it is doing is logical, and we believe it is correct
269 behaviour, although I'm happy to hear reasoned arguments for alterna-
272 T
\bTo
\bot
\bta
\bal
\bls
\bs d
\bdo
\bon
\bn'
\b't
\bt a
\bad
\bdd
\bd u
\bup
\bp
274 There are several reasons why the totals may not appear to add up. The
275 most obvious is having a screen filter in effect, or screen ordering
276 frozen. In this case some captured information is not being shown to
277 you, but is included in the totals.
279 A more subtle explanation comes about when running in promiscuous mode
280 without specifying a -
\b-F
\bF option. In this case there is no easy way to
281 assign the direction of traffic between two third parties. For the
282 purposes of the main display this is done in an arbitrary fashion (by
283 ordering of IP addresses), but for the sake of totals all traffic
284 between other hosts is accounted as incoming, because that's what it is
285 from the point of view of your interface. The -
\b-F
\bF option allows you to
286 specify an arbitrary network boundary, and to show traffic flowing
289 P
\bPe
\bea
\bak
\bk t
\bto
\bot
\bta
\bal
\bls
\bs d
\bdo
\bon
\bn'
\b't
\bt a
\bad
\bdd
\bd u
\bup
\bp
291 Again, this is a feature. The peak sent and peak received didn't nec-
292 essarily happen at the same time. The peak total is the maximum of
293 sent plus received in each captured time division.
295 C
\bCh
\bha
\ban
\bng
\bgi
\bin
\bng
\bg t
\bth
\bhe
\be f
\bfi
\bil
\blt
\bte
\ber
\br c
\bco
\bod
\bde
\be d
\bdo
\boe
\bes
\bsn
\bn'
\b't
\bt s
\bse
\bee
\bem
\bm t
\bto
\bo w
\bwo
\bor
\brk
\bk
297 Give it time. Changing the filter code affects what is captured from
298 the time that you entered it, but most of what is on the display is
299 based on some fraction of the last 40s window of capturing. After
300 changing the filter there may be entries on the display that are disal-
301 lowed by the current filter for up to 40s. DISPLAY FILTERING has imme-
302 diate effect and does not affect what is captured.
306 ~
\b~/
\b/.
\b.i
\bif
\bft
\bto
\bop
\bpr
\brc
\bc
307 Configuration file for iftop.
310 S
\bSE
\bEE
\bE A
\bAL
\bLS
\bSO
\bO
311 t
\btc
\bcp
\bpd
\bdu
\bum
\bmp
\bp(8), p
\bpc
\bca
\bap
\bp(3), d
\bdr
\bri
\bif
\bft
\btn
\bne
\bet
\bt(1).
314 A
\bAU
\bUT
\bTH
\bHO
\bOR
\bR
315 Paul Warren <pdw@ex-parrot.com>
318 V
\bVE
\bER
\bRS
\bSI
\bIO
\bON
\bN
319 $Id: iftop.8,v 1.31 2014/01/05 17:22:39 pdw Exp $
322 C
\bCO
\bOP
\bPY
\bYI
\bIN
\bNG
\bG
323 This program is free software; you can redistribute it and/or modify it
324 under the terms of the GNU General Public License as published by the
325 Free Software Foundation; either version 2 of the License, or (at your
326 option) any later version.
328 This program is distributed in the hope that it will be useful, but
329 WITHOUT ANY WARRANTY; without even the implied warranty of MER-
330 CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
331 Public License for more details.
333 You should have received a copy of the GNU General Public License along
334 with this program; if not, write to the Free Software Foundation, Inc.,
335 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.