iPerf 3 user documentation
Command line option
-p, --port n
The server port for the server to listen on and the client to connect to. This should be the same in both client and server. Default is 5201.
Option to specify the client-side port. (new in iPerf 3.1)
A letter specifying the format to print bandwidth numbers in. Supported formats are
'k' = Kbits/sec 'K' = KBytes/sec
'm' = Mbits/sec 'M' = MBytes/sec
The adaptive formats choose between kilo- and mega- as appropriate.
-i, --interval n
Sets the interval time in seconds between periodic bandwidth, jitter, and loss reports. If non-zero, a report is made every interval seconds of the bandwidth since the last report. If zero, no periodic reports are printed. Default is zero.
-F, --file name
client-side: read from the file and write to the network, instead of using random data;
Set the CPU affinity, if possible (Linux and FreeBSD only). On both the client and server you can set the local affinity by using the n form of this argument (where n is a CPU number). In addition, on the client side you can override the server’s affinity for just that one test, using the n,m form of argument. Note that when using this feature, a process will only be bound to a single CPU (as opposed to a set containing potentialy multiple CPUs).
-B, --bind host
Bind to host, one of this machine's addresses. For the client this sets the outbound interface. For a server this sets the incoming interface. This is only useful on multihomed hosts, which have multiple network interfaces.
give more detailed output
output in JSON format
send output to a log file. (new in iPerf 3.1)
emit debugging output. Primarily (perhaps exclusively) of use to developers.
Show version information and quit.
Show a help synopsis and quit.
SERVER SPECIFIC OPTIONS
Command line option
Run iPerf in server mode. (This will only allow one iperf connection at a time)
Run the server in background as a daemon.
write a file with the process ID, most useful when running as a daemon. (new in iPerf 3.1)
CLIENT SPECIFIC OPTIONS
Command line option
-c, --client host
Run iPerf in client mode, connecting to an iPerf server running on host.
Use SCTP rather than TCP (Linux, FreeBSD and Solaris). (new in iPerf 3.1)
Use UDP rather than TCP. See also the -b option.
Set target bandwidth to n bits/sec (default 1 Mbit/sec for UDP, unlimited for TCP). If there are multiple streams (-P flag), the bandwidth limit is applied separately to each stream. You can also add a ’/’ and a number to the bandwidth specifier. This is called "burst mode". It will send the given number of packets without pausing, even if that temporarily exceeds the specified bandwidth limit.
-t, --time n
-n, --num n[KM]
The number of buffers to transmit. Normally, iPerf sends for 10 seconds. The -n option overrides this and sends an array of len bytes num times, no matter how long that takes. See also the -l, -k and -t options.
-P, --parallel n
The number of simultaneous connections to make to the server. Default is 1.
Run in reverse mode (server sends, client receives).
Sets the socket buffer sizes to the specified value. For TCP, this sets the TCP window size. (this gets sent to the server and used on that side too)
-M, --set-mss n
Attempt to set the TCP maximum segment size (MSS). The MSS is usually the MTU - 40 bytes for the TCP/IP header. For ethernet, the MSS is 1460 bytes (1500 byte MTU).
Set the TCP no delay option, disabling Nagle's algorithm. Normally this is only disabled for interactive applications like telnet.
only use IPv4.
only use IPv6.
-S, --tos n
The type-of-service for outgoing packets. (Many routers ignore the TOS field.) You may specify the value in hex with a '0x' prefix, in octal with a '0' prefix, or in decimal. For example, '0x10' hex = '020' octal = '16' decimal. The TOS numbers specified in RFC 1349 are:
IPTOS_LOWDELAY minimize delay 0x10
IPTOS_THROUGHPUT maximize throughput 0x08
IPTOS_RELIABILITY maximize reliability 0x04
IPTOS_LOWCOST minimize cost 0x02
-L, --flowlabel n
Set the IPv6 flow label (currently only supported on Linux).
Use a "zero copy" method of sending data, such as sendfile(2), instead of the usual write(2). This uses much less CPU.
-O, --omit n
Omit the first n seconds of the test, to skip past the TCP TCP slowstart period.
-T, --title str
Prefix every output line with this string.
-C, --linux-congestion algo
Set the congestion control algorithm (Linux only for iPerf 3.0, Linux and FreeBSD for iPerf 3.1).
See also https://github.com/esnet/iperf