6 iftop - display bandwidth usage on an interface by host
9 S
\bSY
\bYN
\bNO
\bOP
\bPS
\bSI
\bIS
\bS
10 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
11 _
\bn_
\be_
\bt_
\b6/_
\bm_
\ba_
\bs_
\bk_
\b6]
13 D
\bDE
\bES
\bSC
\bCR
\bRI
\bIP
\bPT
\bTI
\bIO
\bON
\bN
14 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
15 interface it can find which looks like an external interface if none is
16 specified, and displays a table of current bandwidth usage by pairs of
17 hosts. i
\bif
\bft
\bto
\bop
\bp must be run with sufficient permissions to monitor all
18 network traffic on the _
\bi_
\bn_
\bt_
\be_
\br_
\bf_
\ba_
\bc_
\be; see p
\bpc
\bca
\bap
\bp(3) for more information, but
19 on most systems this means that it must be run as root.
21 By default, i
\bif
\bft
\bto
\bop
\bp will look up the hostnames associated with addresses
22 it finds in packets. This can cause substantial traffic of itself, and
23 may result in a confusing display. You may wish to suppress display of
24 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
25 off entirely, by using the -
\b-n
\bn option or by pressing r
\br when the program
28 By default, i
\bif
\bft
\bto
\bop
\bp counts all IP packets that pass through the filter,
29 and the direction of the packet is determined according to the direc-
30 tion the packet is moving across the interface. Using the -
\b-F
\bF option it
31 is possible to get i
\bif
\bft
\bto
\bop
\bp to show packets entering and leaving a given
32 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
33 flowing in and out of the 10.* network.
35 Some other filter ideas:
37 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
38 Ignore ethernet broadcast packets.
40 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
41 Count web traffic only, unless it is being directed through a
44 i
\bic
\bcm
\bmp
\bp How much bandwidth are users wasting trying to figure out why
48 O
\bOP
\bPT
\bTI
\bIO
\bON
\bNS
\bS
49 -
\b-h
\bh Print a summary of usage.
51 -
\b-n
\bn Don't do hostname lookups.
53 -
\b-N
\bN Do not resolve port number to service names
55 -
\b-p
\bp Run in promiscuous mode, so that traffic which does not pass
56 directly through the specified interface is also counted.
58 -
\b-P
\bP Turn on port display.
60 -
\b-l
\bl Display and count datagrams addressed to or from link-local IPv6
61 addresses. The default is not to display that address category.
63 -
\b-b
\bb Don't display bar graphs of traffic.
65 -
\b-B
\bB Display bandwidth rates in bytes/sec rather than bits/sec.
67 -
\b-i
\bi _
\bi_
\bn_
\bt_
\be_
\br_
\bf_
\ba_
\bc_
\be
68 Listen to packets on _
\bi_
\bn_
\bt_
\be_
\br_
\bf_
\ba_
\bc_
\be.
70 -
\b-f
\bf _
\bf_
\bi_
\bl_
\bt_
\be_
\br _
\bc_
\bo_
\bd_
\be
71 Use _
\bf_
\bi_
\bl_
\bt_
\be_
\br _
\bc_
\bo_
\bd_
\be to select the packets to count. Only IP packets
72 are ever counted, so the specified code is evaluated as (
\b(_
\bf_
\bi_
\bl_
\bt_
\be_
\br
73 _
\bc_
\bo_
\bd_
\be)
\b) a
\ban
\bnd
\bd i
\bip
\bp.
75 -
\b-F
\bF _
\bn_
\be_
\bt/_
\bm_
\ba_
\bs_
\bk
76 Specifies an IPv4 network for traffic analysis. If specified,
77 iftop will only include packets flowing in to or out of the
78 given network, and packet direction is determined relative to
79 the network boundary, rather than to the interface. You may
80 specify _
\bm_
\ba_
\bs_
\bk as a dotted quad, such as /255.255.255.0, or as a
81 single number specifying the number of bits set in the netmask,
84 -
\b-G
\bG _
\bn_
\be_
\bt_
\b6/_
\bm_
\ba_
\bs_
\bk_
\b6
85 Specifies an IPv6 network for traffic analysis. The value of
86 _
\bm_
\ba_
\bs_
\bk_
\b6 can be given as a prefix length or as a numerical address
87 string for more compound bitmasking.
89 -
\b-c
\bc _
\bc_
\bo_
\bn_
\bf_
\bi_
\bg _
\bf_
\bi_
\bl_
\be
90 Specifies an alternate config file. If not specified, iftop
91 will use ~
\b~/
\b/.
\b.i
\bif
\bft
\bto
\bop
\bpr
\brc
\bc if it exists. See below for a description
95 D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY
96 When running, i
\bif
\bft
\bto
\bop
\bp uses the whole screen to display network usage. At
97 the top of the display is a logarithmic scale for the bar graph which
98 gives a visual indication of traffic.
100 The main part of the display lists, for each pair of hosts, the rate at
101 which data has been sent and received over the preceding 2, 10 and 40
102 second intervals. The direction of data flow is indicated by arrows, <=
103 and =>. For instance,
105 foo.example.com => bar.example.com 1Kb 500b 100b
108 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-
109 p
\bpl
\ble
\be.
\b.c
\bco
\bom
\bm; in the preceding 2 seconds, this averaged 1Kbit/s, around half
110 that amount over the preceding 10s, and a fifth of that over the whole
111 of the last 40s. During each of those intervals, the data sent in the
112 other direction was about 2Mbit/s. On the actual display, part of each
113 line is inverted to give a visual indication of the 10s average of
114 traffic. You might expect to see something like this where host f
\bfo
\boo
\bo is
115 making repeated HTTP requests to b
\bba
\bar
\br, which is sending data back which
116 saturates a 2Mbit/s link.
118 By default, the pairs of hosts responsible for the most traffic (10
119 second average) are displayed at the top of the list.
121 At the bottom of the display, various totals are shown, including peak
122 traffic over the last 40s, total traffic transferred (after filtering),
123 and total transfer rates averaged over 2s, 10s and 40s.
126 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
127 By pressing s
\bs or d
\bd while i
\bif
\bft
\bto
\bop
\bp is running, all traffic for each source
128 or destination will be aggregated together. This is most useful when
129 i
\bif
\bft
\bto
\bop
\bp is run in promiscuous mode, or is run on a gateway machine.
132 P
\bPO
\bOR
\bRT
\bT D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY
133 S
\bS or D
\bD toggle the display of source and destination ports respectively.
134 p
\bp will toggle port display on/off.
137 D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY T
\bTY
\bYP
\bPE
\bE
138 t
\bt cycles through the four line display modes; the default 2-line dis-
139 play, with sent and received traffic on separate lines, and 3 1-line
140 displays, with sent, received, or total traffic shown.
143 D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY O
\bOR
\bRD
\bDE
\bER
\bR
144 By default, the display is ordered according to the 10s average (2nd
145 column). By pressing 1
\b1, 2
\b2 or 3
\b3 it is possible to sort by the 1st, 2nd
146 or 3rd column. By pressing <
\b< or >
\b> the display will be sorted by
147 source or destination hostname respectively.
150 D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY F
\bFI
\bIL
\bLT
\bTE
\bER
\bRI
\bIN
\bNG
\bG
151 l
\bl allows you to enter a POSIX extended regular expression that will be
152 used to filter hostnames shown in the display. This is a good way to
153 quickly limit what is shown on the display. Note that this happens at
154 a much later stage than filter code, and does not affect what is actu-
155 ally captured. Display filters DO NOT affect the totals at the bottom
159 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
160 P
\bP will pause the current display.
162 o
\bo will freeze the current screen order. This has the side effect that
163 traffic between hosts not shown on the screen at the time will not be
164 shown at all, although it will be included in the totals at the bottom
168 S
\bSC
\bCR
\bRO
\bOL
\bLL
\bL D
\bDI
\bIS
\bSP
\bPL
\bLA
\bAY
\bY
169 j
\bj and k
\bk will scroll the display of hosts. This feature is most useful
170 when the display order is frozen (see above).
173 F
\bFI
\bIL
\bLT
\bTE
\bER
\bR C
\bCO
\bOD
\bDE
\bE
174 f
\bf allows you to edit the filter code whilst iftop running. This can
175 lead to some unexpected behaviour.
178 C
\bCO
\bON
\bNF
\bFI
\bIG
\bG F
\bFI
\bIL
\bLE
\bE
179 iftop can read its configuration from a config file. If the -
\b-c
\bc option
180 is not specified, iftop will attempt to read its configuration from
181 ~
\b~/
\b/.
\b.i
\bif
\bft
\bto
\bop
\bpr
\brc
\bc, if it exists. Any command line options specified will
182 override settings in the config file.
184 The config file consists of one configuration directive per line. Each
185 directive is a name value pair, for example:
189 sets the network interface. The following config directives are sup-
193 i
\bin
\bnt
\bte
\ber
\brf
\bfa
\bac
\bce
\be:
\b: _
\bi_
\bf
194 Sets the network interface to _
\bi_
\bf.
196 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)
197 Controls reverse lookup of IP addresses.
199 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)
200 Controls conversion of port numbers to service names.
202 f
\bfi
\bil
\blt
\bte
\ber
\br-
\b-c
\bco
\bod
\bde
\be:
\b: _
\bb_
\bp_
\bf
203 Sets the filter code to _
\bb_
\bp_
\bf.
205 s
\bsh
\bho
\bow
\bw-
\b-b
\bba
\bar
\brs
\bs:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
206 Controls display of bar graphs.
208 p
\bpr
\bro
\bom
\bmi
\bis
\bsc
\bcu
\buo
\bou
\bus
\bs:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
209 Puts the interface into promiscuous mode.
211 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)
212 Controls display of port numbers.
214 l
\bli
\bin
\bnk
\bk-
\b-l
\blo
\boc
\bca
\bal
\bl:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
215 Determines displaying of link-local IPv6 addresses.
217 h
\bhi
\bid
\bde
\be-
\b-s
\bso
\bou
\bur
\brc
\bce
\be:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
218 Hides source host names.
220 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)
221 Hides destination host names.
223 u
\bus
\bse
\be-
\b-b
\bby
\byt
\bte
\bes
\bs:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
224 Use bytes for bandwidth display, rather than bits.
226 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)
227 Sets which column is used to sort the display.
229 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)
230 Controls the appearance of each item in the display.
232 s
\bsh
\bho
\bow
\bw-
\b-t
\bto
\bot
\bta
\bal
\bls
\bs:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
233 Shows cumulative total for each item.
235 l
\blo
\bog
\bg-
\b-s
\bsc
\bca
\bal
\ble
\be:
\b: _
\b(_
\by_
\be_
\bs_
\b|_
\bn_
\bo_
\b)
236 Use a logarithmic scale for bar graphs.
238 m
\bma
\bax
\bx-
\b-b
\bba
\ban
\bnd
\bdw
\bwi
\bid
\bdt
\bth
\bh:
\b: _
\bb_
\bw
239 Fixes the maximum for the bar graph scale to _
\bb_
\bw, e.g. "10M".
240 Note that the value has to always be in bits, regardless if the
241 option to display in bytes has been chosen.
243 n
\bne
\bet
\bt-
\b-f
\bfi
\bil
\blt
\bte
\ber
\br:
\b: _
\bn_
\be_
\bt_
\b/_
\bm_
\ba_
\bs_
\bk
244 Defines an IP network boundary for determining packet direction.
246 n
\bne
\bet
\bt-
\b-f
\bfi
\bil
\blt
\bte
\ber
\br6
\b6:
\b: _
\bn_
\be_
\bt_
\b6_
\b/_
\bm_
\ba_
\bs_
\bk_
\b6
247 Defines an IPv6 network boundary for determining packet direc-
250 s
\bsc
\bcr
\bre
\bee
\ben
\bn-
\b-f
\bfi
\bil
\blt
\bte
\ber
\br:
\b: _
\br_
\be_
\bg_
\be_
\bx_
\bp
251 Sets a regular expression to filter screen output.
254 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)
255 There are some circumstances in which iftop may not do what you expect.
256 In most cases what it is doing is logical, and we believe it is correct
257 behaviour, although I'm happy to hear reasoned arguments for alterna-
260 T
\bTo
\bot
\bta
\bal
\bls
\bs d
\bdo
\bon
\bn'
\b't
\bt a
\bad
\bdd
\bd u
\bup
\bp
262 There are several reasons why the totals may not appear to add up. The
263 most obvious is having a screen filter in effect, or screen ordering
264 frozen. In this case some captured information is not being shown to
265 you, but is included in the totals.
267 A more subtle explanation comes about when running in promiscuous mode
268 without specifying a -
\b-F
\bF option. In this case there is no easy way to
269 assign the direction of traffic between two third parties. For the
270 purposes of the main display this is done in an arbitrary fashion (by
271 ordering of IP addresses), but for the sake of totals all traffic
272 between other hosts is accounted as incoming, because that's what it is
273 from the point of view of your interface. The -
\b-F
\bF option allows you to
274 specify an arbitrary network boundary, and to show traffic flowing
277 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
279 Again, this is a feature. The peak sent and peak received didn't nec-
280 essarily happen at the same time. The peak total is the maximum of
281 sent plus received in each captured time division.
283 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
285 Give it time. Changing the filter code affects what is captured from
286 the time that you entered it, but most of what is on the display is
287 based on some fraction of the last 40s window of capturing. After
288 changing the filter there may be entries on the display that are disal-
289 lowed by the current filter for up to 40s. DISPLAY FILTERING has imme-
290 diate effect and does not affect what is captured.
294 ~
\b~/
\b/.
\b.i
\bif
\bft
\bto
\bop
\bpr
\brc
\bc
295 Configuration file for iftop.
298 S
\bSE
\bEE
\bE A
\bAL
\bLS
\bSO
\bO
299 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).
302 A
\bAU
\bUT
\bTH
\bHO
\bOR
\bR
303 Paul Warren <pdw@ex-parrot.com>
306 V
\bVE
\bER
\bRS
\bSI
\bIO
\bON
\bN
307 $Id: iftop.8,v 1.27 2010/11/27 11:06:12 pdw Exp $
310 C
\bCO
\bOP
\bPY
\bYI
\bIN
\bNG
\bG
311 This program is free software; you can redistribute it and/or modify it
312 under the terms of the GNU General Public License as published by the
313 Free Software Foundation; either version 2 of the License, or (at your
314 option) any later version.
316 This program is distributed in the hope that it will be useful, but
317 WITHOUT ANY WARRANTY; without even the implied warranty of MER-
318 CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
319 Public License for more details.
321 You should have received a copy of the GNU General Public License along
322 with this program; if not, write to the Free Software Foundation, Inc.,
323 675 Mass Ave, Cambridge, MA 02139, USA.