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IPERF(1) User Manuals IPERF(1)


iperf - perform network throughput tests


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).


-b, --bandwidth
set the target bandwidth (and optional standard devation where supported)
-e, --enhanced
Display enhanced output in reports otherwise use legacy report (ver 2.0.5) formatting (see notes)
-f, --format
[abkmgBKMG] format to report: adaptive, bits, Bytes, Kbits, Mbits, Gbits, KBytes, MBytes, GBytes (see NOTES for more)
-h, --help
print a help synopsis
-i, --interval n
pause n seconds between periodic bandwidth reports
-l, --len n[kmKM]
set read/write buffer size (TCP) or length (UDP) to n (TCP default 128K, UDP default 1470)
perform layer 2 length checks on received UDP packets (requires systems that support packet sockets, e.g. Linux)
-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
use 64 bit UDP sequence numbers
-w, --window n[kmKM]
TCP window size (socket buffer size)
-z, --realtime
Request realtime scheduler, if supported.
-B, --bind host
bind to host, ip address or multicast address and optional port (see notes)
-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
-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)


-b, --bandwidth n[kmgKMG]
set target read rate to n bits/sec. TCP only for the server.
-s, --server
run in server mode
output UDP latency histograms, bin width (default 1 millisecond, append u for microseconds,) bincount is total bins (default 1000), ci is confidence interval between 0-100% (default lower 5%, upper 95%)
-B, --bind ip | ip%device
bind src ip addr and optional src device for receiving
-D, --daemon
run the server as a daemon. On Windows this will also install the IPerfService.
-H, --ssm-host host
Set the source host (ip addr) per SSM multicast, i.e. the S of the S,G
-R, --remove
remove the IPerfService (Windows only).
-U, --single_udp
run in single threaded UDP mode
-V, --ipv6_domain
Enable IPv6 reception by setting the domain and socket to AF_INET6 (Can receive on both IPv4 and IPv6)


-b, --bandwidth n[kmgKMG] | npps
set target bandwidth to n bits/sec (default 1 Mbit/sec) or n packets per sec. This may be used with TCP or UDP. For variable loads use format mean,standard deviation
-c, --client host
run in client mode, connecting to host
-d, --dualtest
Do a bidirectional test simultaneously
increment the destination ip address when using the parallel (-P) option
--ipg n
set the interpacket gap to n (units of milliseconds) for packets within an isochronous frame (burst), requires --isochronous
send isochronous traffic with frequency frames per second and load defined by mean and standard deviation using a log normal distribution, defaults to 60:20m,0
-n, --num n[kmKM]
number of bytes to transmit (instead of -t)
-r, --tradeoff
Do a bidirectional test individually
-t, --time n
time in seconds to listen for new traffic connections, receive traffic or transmit traffic (Defaults: transmit is 10 secs while listen and receive are indefinite)
--tx-sync n
set the tx-sync interval to n (units of seconds) for synchronized packet writes
-B, --bind ip | ip:port | ipv6 -V | [ipv6]:port -V
bind src ip addr and optional port as the source of traffic (see notes)
-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
-R, --reverse
reverse the traffic flow after header exchange, useful for testing through firewalls
-S, --tos
set the socket's IP_TOS (byte) field
-T, --ttl n
time-to-live, for multicast (default 1) -V, --ipv6_domain Set the domain to IPv6 (send packets over IPv6)
-X, --peerdetect
run server version detection prior to traffic.
-Z, --linux-congestion algo
set TCP congestion control algorithm (Linux only)


Controls the size of TCP buffers.


Some numeric options support format characters per '<value>c' (e.g. 10M) where the c format characters are k,m,g,K,M,G. Lowercase format characters are 10^3 based and uppercase are 2^n based, e.g. 1k = 1000, 1K = 1024, 1m = 1,000,000 and 1M = 1,048,576
The -b option supports variable offered loads through the <mean>,<standard deviation> format, e.g. -b 100m,10m on the client. The distribution used is log normal. Similar for the isochronous option.
The -e or --enhanced latency output on the UDP servers assumes the clients' and servers' system clocks are synchronized. Network Time Protocol (NTP) or Precision Time Protocol (PTP) are commonly used for this. The reference clock(s) or oscillator's error will also affect the accuracy of UDP latency measurements.
The -B option affects the bind() system call. This is typically used to bind to a particular IP address. Only packets destined to that IP address will be received while any transmitted packets will carry that IP address as their source. The bind() does not control anything about the routing of transmitted packets. So, for example, if the IP address of eth0 is used for -B and the routing table for the destination IP address (per -c) resolves the output interface to be eth1, then the host will send the packet out device eth1 with the source IP address of eth0. To affect the physical output interface (e.g. dual homed systems) the host's routing table(s) need to be configured, e.g. configure policy routing per each -B source address.


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Iperf2, based from iperf (originally written by Mark Gates and Alex Warshavsky), has a goal of maintenance with some feature enhancement. Other contributions from Ajay Tirumala, Jim Ferguson, Jon Dugan <jdugan at x1024 dot net>, Feng Qin, Kevin Gibbs, John Estabrook <jestabro at>, Andrew Gallatin <gallatin at>, Stephen Hemminger <shemminger at>, Tim Auckland, Robert J. McMahon <rjmcmahon at>