iperf -s [ options ]

iperf -c server [ options ]

iperf -u -s [ options ]

iperf -u -c server [ options ]


iperf is a tool for performing network throughput measurements. It can test either TCP or UDP throughput. To perform an iperf test the user must establish both a server (to discard traffic) and a client (to generate traffic).


-f, --format

[kmKM] format to report: Kbits, Mbits, KBytes, MBytes

-h, --help

print a help synopsis

-i, --interval n

pause n seconds between periodic bandwidth reports

-l, --len n[KM]

set length read/write buffer to n (default 8 KB)

-m, --print_mss

print TCP maximum segment size (MTU - TCP/IP header)

-o, --output <filename>

output the report or error message to this specified file

-p, --port n

set server port to listen on/connect to to n (default 5001)

-u, --udp

use UDP rather than TCP

-w, --window n[KM]

TCP window size (socket buffer size)

-B, --bind <host>

bind to <host>, an interface or multicast address

-C, --compatibility

for use with older versions does not sent extra msgs

-M, --mss n

set TCP maximum segment size (MTU - 40 bytes)

-N, --nodelay

set TCP no delay, disabling Nagle's Algorithm

-v, --version

print version information and quit

-V, --IPv6Version

Set the domain to IPv6

-x, --reportexclude

[CDMSV] exclude C(connection) D(data) M(multicast) S(settings) V(server) reports

-y, --reportstyle C|c

if set to C or c report results as CSV (comma separated values)


-s, --server

run in server mode

-U, --single_udp

run in single threaded UDP mode

-D, --daemon

run the server as a daemon


-b, --bandwidth n[KM]

set target bandwidth to n bits/sec (default 1 Mbit/sec). This setting requires UDP (-u).

-c, --client <host>

run in client mode, connecting to <host>

-d, --dualtest

Do a bidirectional test simultaneously

-n, --num n[KM]

number of bytes to transmit (instead of -t)

-r, --tradeoff

Do a bidirectional test individually

-t, --time n

time in seconds to transmit for (default 10 secs)

-F, --fileinput <name>

input the data to be transmitted from a file

-I, --stdin

input the data to be transmitted from stdin

-L, --listenport n

port to receive bidirectional tests back on

-P, --parallel n

number of parallel client threads to run

-T, --ttl n

time-to-live, for multicast (default 1)

-Z, --linux-congestion <algo>

set TCP congestion control algorithm (Linux only)



Controls the size of TCP buffers.


This section needs to be filled in.


Exit statuses are inconsistent. The threading implementation is rather heinous.


Iperf was originally written by Mark Gates and Alex Warshavsky. Man page and maintence by Jon Dugan <jdugan at x1024 dot net>. Other contributions from Ajay Tirumala, Jim Ferguson, Feng Qin, Kevin Gibbs, John Estabrook <jestabro at>, Andrew Gallatin <gallatin at>, Stephen Hemminger <shemminger at>