Ubuntu 22.04 iperf3 安装与命令参数详解
在 Ubuntu 22.04 上在线/离线安装 iperf3 3.9 并逐参数实测客户端与服务端命令输入与回显，涵盖 -c/-P/-u/-b/-R/-t/-i/-w/-l/-p/-O 与 -J JSON 输出。
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Ubuntu 22.04 iperf3 安装与命令参数详解
目标：在 Ubuntu 22.04 上安装 iperf3 3.9，并逐参数实测客户端/服务端带宽测试命令的输入与回显，涵盖在线 apt / 离线 deb 两种安装方式，以及
-c、-P、-u、-b、-R、-t/-i、-w、-l、-p、-O、-J等参数。本文命令与输出均为 Ubuntu 22.04（iperf3 3.9，Debian 包3.9-1+deb11u1ubuntu0.1）双机实测回显。
一、环境信息
- 操作系统：Ubuntu 22.04 LTS
- iperf3 版本：3.9（包
iperf3 3.9-1+deb11u1ubuntu0.1 amd64，依赖libiperf0同版本） - 本机（测试客户端）：eth0，IP
172.27.0.3，同属172.27.0.0/16内网 - 对端主机（测试服务端）：IP
172.27.0.2，监听 5201 端口 - 双向 TCP/UDP 均在同一内网段，路径无 NAT，实测吞吐约 30~35 Gbits/sec
- 服务端后台守护进程 PID 文件：
/tmp/iperf3.pid
二、工具概述
iperf3 是新一代的带宽/吞吐量测试工具，在单条 TCP/UDP 连接（默认）或多条并行连接上以固定间隔周期性上报吞吐、重传、拥塞窗口等指标，广泛用于验证网卡、交换机、链路带宽与 QoS 限速配置。它采用「服务端 + 客户端」主从模型：服务端 -s 监听端口等待连接，客户端 -c <host> 发起连接并发送/接收数据。支持 TCP、UDP、SCTP，可指定时长（-t）、间隔（-i）、限速（-b）、并行流（-P）、反向（-R）以及 JSON 结构化输出（-J）。本文针对 Ubuntu 22.04 上的 3.9 实测。
三、安装
3.1 在线安装（apt）
sudo apt update
sudo apt install -y iperf3
💡 Ubuntu 22.04 仓库中的
iperf3依赖libiperf0，安装时会一并自动安装；运行版本为iperf 3.9。
安装后验证（包管理视角）：
dpkg -l iperf3
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-======================-============-==========================================
ii iperf3 3.9-1+deb11u1ubuntu0.1 amd64 Internet Protocol bandwidth measuring tool
版本号（二进制视角，-v）：
iperf3 -v
iperf 3.9 (cJSON 1.7.13)
Linux 172.27.0.3 6.8.0-138-generic #138~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Aug 7 13:43:15 UTC x86_64
Optional features available: CPU affinity setting, IPv6 flow label, SCTP, TCP congestion algorithm setting, sendfile / zerocopy, socket pacing, authentication
3.2 离线安装（.deb 包）
在可联网的 Ubuntu 机器上下载 iperf3 及其依赖：
mkdir -p /opt/data/iperf3
cd /opt/data/iperf3
apt download iperf3 libiperf0
WARNING: apt does not have a stable CLI interface. Use with caution in scripts.
Get:1 http://archive.ubuntu.com/ubuntu jammy-updates/universe amd64 iperf3 amd64 3.9-1+deb11u1ubuntu0.1 [14.6 kB]
Get:2 http://archive.ubuntu.com/ubuntu jammy-updates/universe amd64 libiperf0 amd64 3.9-1+deb11u1ubuntu0.1 [82.8 kB]
Fetched 97.4 kB in 1s (67.0 kB/s)
下载得到两个 deb 包：
iperf3_3.9-1+deb11u1ubuntu0.1_amd64.deb
libiperf0_3.9-1+deb11u1ubuntu0.1_amd64.deb
拷贝到离线机器后一键安装：
dpkg -i /opt/data/iperf3/*.deb
安装后验证：
iperf3 -v | head -1
iperf 3.9 (cJSON 1.7.13)
⚠️ 安装过程若提示依赖缺失，先执行
apt-get install -f补齐依赖后再dpkg -i。
四、命令实测
4.1 服务端启动 —— iperf3 -s
用途：在服务端监听 5201 端口等待客户端接入。前台运行时会打印「Server listening」横幅，并在每次接入后回报传输数据。
iperf3 -s
服务端前台真实回显（本机 172.27.0.2，接收来自客户端 172.27.0.3 的一次 2 秒 TCP 测试）：
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 172.27.0.3, port 59784
[ 5] local 172.27.0.2 port 5201 connected to 172.27.0.3 port 59786
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 3.95 GBytes 33.9 Gbits/sec
[ 5] 1.00-2.00 sec 4.09 GBytes 35.1 Gbits/sec
[ 5] 2.00-12.05 sec 136 MBytes 113 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-12.05 sec 8.17 GBytes 5.83 Gbits/sec receiver
后台守护运行（-s -D 以守护进程方式启动，-I 指定 PID 文件，脱离终端常驻）：
iperf3 -s -D -I /tmp/iperf3.pid
💡
-D（daemon）使服务端后台常驻，适合长期提供服务；结合-1（one-off）可实现「处理一次连接后自动退出」的一次性服务。
4.2 客户端基础 TCP 测试 —— iperf3 -c 172.27.0.2
用途：客户端向服务端 172.27.0.2:5201 发起默认 10 秒的 TCP 上行测速。
参数说明：-c <host> 指定目标服务端；默认协议为 TCP、时长 10 秒（-t 默认值）、间隔 1 秒刷新一次（-i 默认 1）。
iperf3 -c 172.27.0.2
Connecting to host 172.27.0.2, port 5201
[ 5] local 172.27.0.3 port 42088 connected to 172.27.0.2 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 4.02 GBytes 34.5 Gbits/sec 3 2.74 MBytes
[ 5] 1.00-2.00 sec 4.04 GBytes 34.7 Gbits/sec 2 2.75 MBytes
[ 5] 2.00-3.00 sec 4.14 GBytes 35.6 Gbits/sec 1 2.75 MBytes
[ 5] 3.00-4.00 sec 3.60 GBytes 30.9 Gbits/sec 0 2.91 MBytes
[ 5] 4.00-5.00 sec 4.15 GBytes 35.7 Gbits/sec 1 2.91 MBytes
[ 5] 5.00-6.00 sec 4.10 GBytes 35.2 Gbits/sec 1 2.92 MBytes
[ 5] 6.00-7.00 sec 4.03 GBytes 34.6 Gbits/sec 0 2.92 MBytes
[ 5] 7.00-8.00 sec 3.91 GBytes 33.6 Gbits/sec 0 2.94 MBytes
[ 5] 8.00-9.00 sec 4.11 GBytes 35.3 Gbits/sec 0 2.94 MBytes
[ 5] 9.00-10.00 sec 3.91 GBytes 33.5 Gbits/sec 1 2.94 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 40.0 GBytes 34.4 Gbits/sec 9 sender
[ 5] 0.00-10.04 sec 40.0 GBytes 34.2 Gbits/sec receiver
iperf Done.
解读：首行 Connecting to host 172.27.0.2, port 5201 明确连接目标与端口；第二行 [ 5] local 172.27.0.3 port 42088 connected to 172.27.0.2 port 5201 为分配的连接 socket 信息（客户端源端口 42088）。中间每行是 1 秒间隔的瞬时吞吐（36GB 量级偏差来自拥塞窗口 Cwnd 的动态调整），Retr 为重传次数。底部汇总行 0.00-10.00 为整个测试期间的平均值：发送方向 40.0 GBytes / 34.4 Gbits/sec，接收方向 40.0 GBytes / 34.2 Gbits/sec。iperf Done. 表示测试正常结束（返回码 0）。
4.3 并行数据流 —— iperf3 -c 172.27.0.2 -P 4
用途：用 4 条并行 TCP 连接同时测速，模拟多连接/多核并发场景，检验单条连接之外的聚合带宽上限。
参数说明：-P <n> 指定并行流数（默认 1）。
iperf3 -c 172.27.0.2 -P 4 -t 4 -i 1
Connecting to host 172.27.0.2, port 5201
[ 5] local 172.27.0.3 port 53930 connected to 172.27.0.2 port 5201
[ 7] local 172.27.0.3 port 53938 connected to 172.27.0.2 port 5201
[ 9] local 172.27.0.3 port 53942 connected to 172.27.0.2 port 5201
[ 11] local 172.27.0.3 port 53956 connected to 172.27.0.2 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 966 MBytes 8.10 Gbits/sec 1 7.39 MBytes
[ 7] 0.00-1.00 sec 966 MBytes 8.10 Gbits/sec 0 10.3 MBytes
[ 9] 0.00-1.00 sec 966 MBytes 8.10 Gbits/sec 3 4.62 MBytes
[ 11] 0.00-1.00 sec 965 MBytes 8.09 Gbits/sec 0 10.3 MBytes
[SUM] 0.00-1.00 sec 3.77 GBytes 32.4 Gbits/sec 4
- - - - - - - - - - - - - - - - - - - - - - - - -
[ 5] 1.00-2.00 sec 998 MBytes 8.37 Gbits/sec 2 7.39 MBytes
[ 7] 1.00-2.00 sec 998 MBytes 8.37 Gbits/sec 141 10.3 MBytes
[ 9] 1.00-2.00 sec 998 MBytes 8.37 Gbits/sec 5 3.23 MBytes
[ 11] 1.00-2.00 sec 998 MBytes 8.37 Gbits/sec 2 10.3 MBytes
[SUM] 1.00-2.00 sec 3.90 GBytes 33.5 Gbits/sec 150
- - - - - - - - - - - - - - - - - - - - - - - - -
[ 5] 2.00-3.00 sec 1.01 GBytes 8.67 Gbits/sec 1 7.39 MBytes
[ 7] 2.00-3.00 sec 1.01 GBytes 8.67 Gbits/sec 2 10.3 MBytes
[ 9] 2.00-3.00 sec 1.01 GBytes 8.67 Gbits/sec 2 3.23 MBytes
[ 11] 2.00-3.00 sec 1.01 GBytes 8.67 Gbits/sec 2 10.3 MBytes
[SUM] 2.00-3.00 sec 4.04 GBytes 34.7 Gbits/sec 7
- - - - - - - - - - - - - - - - - - - - - - - - -
[ 5] 3.00-4.00 sec 1.10 GBytes 9.42 Gbits/sec 0 7.39 MBytes
[ 7] 3.00-4.00 sec 1.10 GBytes 9.42 Gbits/sec 2 10.3 MBytes
[ 9] 3.00-4.00 sec 1.09 GBytes 9.39 Gbits/sec 0 3.23 MBytes
[ 11] 3.00-4.00 sec 1.10 GBytes 9.43 Gbits/sec 1 10.3 MBytes
[SUM] 3.00-4.00 sec 4.38 GBytes 37.7 Gbits/sec 3
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-4.00 sec 4.02 GBytes 8.64 Gbits/sec 4 sender
[ 5] 0.00-4.04 sec 4.02 GBytes 8.56 Gbits/sec receiver
[ 7] 0.00-4.00 sec 4.02 GBytes 8.64 Gbits/sec 145 sender
[ 7] 0.00-4.04 sec 4.02 GBytes 8.56 Gbits/sec receiver
[ 9] 0.00-4.00 sec 4.02 GBytes 8.63 Gbits/sec 10 sender
[ 9] 0.00-4.04 sec 4.02 GBytes 8.55 Gbits/sec receiver
[ 11] 0.00-4.00 sec 4.02 GBytes 8.64 Gbits/sec 5 sender
[ 11] 0.00-4.04 sec 4.02 GBytes 8.56 Gbits/sec receiver
[SUM] 0.00-4.00 sec 16.1 GBytes 34.6 Gbits/sec 164 sender
[SUM] 0.00-4.04 sec 16.1 GBytes 34.2 Gbits/sec receiver
iperf Done.
解读：4 条连接各分配一个 [ 5]/[ 7]/[ 9]/[ 11] 标识行，[SUM] 为四条流的聚合行。每条流约 8.6 Gbits/sec，聚合 [SUM] 16.1 GBytes / 34.6 Gbits/sec，与单流 34.4 Gbits/sec 相当——说明本机链路瓶颈不在单连接，而在总带宽（网卡/共享内核转发能力）。
4.4 UDP 模式 —— iperf3 -c 172.27.0.2 -u -b 200M
用途：UDP 测速重点评估抖动（Jitter）、丢包率，适合模拟语音/视频等实时流量。
参数说明：-u 改用 UDP；-b 200M 指定目标发送速率（UDP 默认 1 Mbit/sec，必须显式给定额度）。
iperf3 -c 172.27.0.2 -u -b 200M -t 3
Connecting to host 172.27.0.2, port 5201
[ 5] local 172.27.0.3 port 33328 connected to 172.27.0.2 port 5201
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 23.8 MBytes 200 Mbits/sec 17252
[ 5] 1.00-2.00 sec 23.8 MBytes 200 Mbits/sec 17265
[ 5] 2.00-3.00 sec 23.8 MBytes 200 Mbits/sec 17265
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-3.00 sec 71.5 MBytes 200 Mbits/sec 0.000 ms 0/51782 (0%) sender
[ 5] 0.00-3.04 sec 71.5 MBytes 197 Mbits/sec 0.002 ms 0/51782 (0%) receiver
iperf Done.
解读：UDP 模式下每行多出 Total Datagrams（数据报数）与汇总行的 Jitter（抖动）和 Lost/Total Datagrams（丢包/总报文）。本例发送 200 Mbits/sec、共 51782 个报文，接收端抖动 0.002 ms、丢包 0/51782（0%），说明链路无拥塞、无丢包。
4.5 限速测试 —— iperf3 -c 172.27.0.2 -b 1G
用途：TCP 模式下用 -b 限速，验证链路/QoS 对限速额度的响应与丢包重传表现。
参数说明：-b <rate> 在 TCP 下限制发送速率，在 UDP 下为目标发送速率；可带 K/M/G 后缀。
iperf3 -c 172.27.0.2 -b 1G -t 3
Connecting to host 172.27.0.2, port 5201
[ 5] local 172.27.0.3 port 46600 connected to 172.27.0.2 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 119 MBytes 999 Mbits/sec 0 272 KBytes
[ 5] 1.00-2.00 sec 119 MBytes 1.00 Gbits/sec 0 329 KBytes
[ 5] 2.00-3.00 sec 119 MBytes 1.00 Gbits/sec 0 329 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-3.00 sec 358 MBytes 1000 Mbits/sec 0 sender
[ 5] 0.00-3.04 sec 358 MBytes 987 Mbits/sec receiver
iperf Done.
解读：-b 1G 将发送速率稳定压制在 999~1000 Mbits/sec，Retr 为 0，说明 QoS 限速生效且未引发丢包重传。对比 4.2 无限制时 34.4 Gbits/sec，-b 精确控制了发送速率——常用于验证带宽整形/限速策略。
4.6 反向模式 —— iperf3 -c 172.27.0.2 -R
用途：缺省为客户端 → 服务端发送；-R 反转为「服务端发送、客户端接收」，用于测试下行带宽。
参数说明：-R 使服务端变成发送方。
iperf3 -c 172.27.0.2 -R -t 4 -i 1
Connecting to host 172.27.0.2, port 5201
Reverse mode, remote host 172.27.0.2 is sending
[ 5] local 172.27.0.3 port 40126 connected to 172.27.0.2 port 5201
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 3.80 GBytes 32.7 Gbits/sec
[ 5] 1.00-2.00 sec 3.64 GBytes 31.3 Gbits/sec
[ 5] 2.00-3.00 sec 4.04 GBytes 34.7 Gbits/sec
[ 5] 3.00-4.00 sec 3.99 GBytes 34.3 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-4.04 sec 15.5 GBytes 32.9 Gbits/sec 49 sender
[ 5] 0.00-4.00 sec 15.5 GBytes 33.2 Gbits/sec receiver
iperf Done.
解读：输出首行 Reverse mode, remote host 172.27.0.2 is sending 提示反向模式；本次下行平均 32.9 Gbits/sec（sender 指服务端）。-R 与 -P、-b 等常组合使用。
4.7 时长与间隔 —— iperf3 -c 172.27.0.2 -t 3 -i 1
用途：-t 控制测试秒数（默认 10），-i 控制周期报告间隔秒数（默认 1），用更短时长快速完成功能验证。
参数说明：-t <sec> 测试时长；-i <sec> 周期上报间隔。
iperf3 -c 172.27.0.2 -t 3 -i 1
Connecting to host 172.27.0.2, port 5201
[ 5] local 172.27.0.3 port 40158 connected to 172.27.0.2 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 3.63 GBytes 31.2 Gbits/sec 1 3.07 MBytes
[ 5] 1.00-2.00 sec 3.60 GBytes 30.9 Gbits/sec 0 3.07 MBytes
[ 5] 2.00-3.00 sec 3.78 GBytes 32.5 Gbits/sec 2 3.07 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-3.00 sec 11.0 GBytes 31.5 Gbits/sec 3 sender
[ 5] 0.00-3.04 sec 11.0 GBytes 31.0 Gbits/sec receiver
iperf Done.
解读：-t 3 -i 1 只跑 3 秒、每 1 秒出一次报告，运行更快；脚本循环采集时可用更小的 -i 提高采样密度。也支持用 -n <bytes>（按字节）或 -k <count>（按报文数）替代 -t 控制测试量。
4.8 接收/发送窗口 —— iperf3 -c 172.27.0.2 -w 1M（含报错处理）
用途：-w 设置 socket 发送/接收缓冲区（窗口）大小，用于长肥管道（高带宽高延迟）场景下提升吞吐。
参数说明：-w <size> 设定窗口/套接字缓冲区大小，可带 K/M/G 后缀。
实测回显（-w 1M 报错）：
iperf3 -c 172.27.0.2 -w 1M -t 3
iperf3: error - socket buffer size not set correctly
Connecting to host 172.27.0.2, port 5201
解读与解决：报 socket buffer size not set correctly 说明请求的 -w 值超过了系统套接字缓冲区上限（Linux 默认 net.core.wmem_max/net.core.rmem_max 约 212992 字节）。改用不超过上限的取值即可正常执行，例如 -w 200K：
iperf3 -c 172.27.0.2 -w 200K -t 2
Connecting to host 172.27.0.2, port 5201
[ 5] local 172.27.0.3 port 40154 connected to 172.27.0.2 port 5201
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-2.00 sec 6.35 GBytes 27.3 Gbits/sec 43 sender
[ 5] 0.00-2.04 sec 6.35 GBytes 26.7 Gbits/sec receiver
iperf Done.
如需更大的 -w，需先调高内核参数（真实服务器上执行，重启后仍生效可持久化到 /etc/sysctl.conf）：
sudo sysctl -w net.core.wmem_max=1048576 net.core.rmem_max=1048576
4.9 缓冲区长度 —— iperf3 -c 172.27.0.2 -l 64K
用途：-l 指定单次读写的缓冲区/报文长度。TCP 默认 128 KB；调整后可观察不同报文分节对吞吐的影响。
参数说明：-l <len> 设置读写缓冲区长度。
iperf3 -c 172.27.0.2 -l 64K -t 3
Connecting to host 172.27.0.2, port 5201
[ 5] local 172.27.0.3 port 40158 connected to 172.27.0.2 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 3.39 GBytes 29.1 Gbits/sec 0 3.07 MBytes
[ 5] 1.00-2.00 sec 3.63 GBytes 31.2 Gbits/sec 0 3.07 MBytes
[ 5] 2.00-3.00 sec 3.60 GBytes 30.9 Gbits/sec 49 3.07 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-3.00 sec 10.6 GBytes 30.4 Gbits/sec 49 sender
[ 5] 0.00-3.04 sec 10.6 GBytes 30.0 Gbits/sec receiver
iperf Done.
解读：改用 64 KB 缓冲后平均 30.4 Gbits/sec，与默认 128 KB 的 31~34 Gbits/sec 相当，说明本机场景下缓冲长度对吞吐影响有限。
4.10 自定义端口 —— iperf3 -c 172.27.0.2 -p 5202
用途：默认服务端监听/客户端连接 5201；-p 可指定其他端口，便于多实例、多场景并存。
参数说明：客户端 -p <port> 与 -c 连目标端口；服务端需先用 iperf3 -s -p 5202 在同端口监听。
服务端用 5202 端口监听：
iperf3 -s -p 5202
客户端连接 172.27.0.2:5202：
iperf3 -c 172.27.0.2 -p 5202 -t 3
Connecting to host 172.27.0.2, port 5202
[ 5] local 172.27.0.3 port 49296 connected to 172.27.0.2 port 5202
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 3.90 GBytes 33.5 Gbits/sec 0 3.83 MBytes
[ 5] 1.00-2.00 sec 3.90 GBytes 33.5 Gbits/sec 2 3.83 MBytes
[ 5] 2.00-3.00 sec 3.94 GBytes 33.9 Gbits/sec 192 3.83 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-3.00 sec 11.7 GBytes 33.6 Gbits/sec 194 sender
[ 5] 0.00-13.04 sec 11.7 GBytes 7.73 Gbits/sec receiver
iperf Done.
解读：首行 port 5202 确认连到自定义端口；其余输出结构与 5201 一致。注意同一端口只能被一个服务端实例占用。
4.11 省略起始段 —— iperf3 -c 172.27.0.2 -O 1
用途：-O N 在统计中省略前 N 秒，避开枚举/建链/拥塞窗口爬升等「预热期」，让平均吞吐更能体现稳定状态。
参数说明：-O <N> 报告时省略前 N 秒（不影响总时长）。
iperf3 -c 172.27.0.2 -O 1 -t 4 -i 1
Connecting to host 172.27.0.2, port 5201
[ 5] local 172.27.0.3 port 56812 connected to 172.27.0.2 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 3.75 GBytes 32.2 Gbits/sec 1 3.90 MBytes (omitted)
[ 5] 0.00-1.00 sec 3.78 GBytes 32.5 Gbits/sec 1 3.90 MBytes
[ 5] 1.00-2.00 sec 3.94 GBytes 33.9 Gbits/sec 1 3.90 MBytes
[ 5] 2.00-3.00 sec 4.06 GBytes 34.9 Gbits/sec 1 3.90 MBytes
[ 5] 3.00-4.00 sec 4.12 GBytes 35.4 Gbits/sec 0 3.90 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-4.00 sec 15.9 GBytes 34.1 Gbits/sec 3 sender
[ 5] 0.00-14.05 sec 16.0 GBytes 9.81 Gbits/sec receiver
iperf Done.
解读：第 1 秒的间隔行被标记为 (omitted)（仅显示、不参与平均），其余行正常上报。
4.12 JSON 结构化输出 —— iperf3 -c 172.27.0.2 -J
用途：-J 以 JSON 输出完整结果，机器可解析，方便脚本/监控系统消费；--logfile <file> 可将日志写入文件，配合 --forceflush 每次间隔实时落盘。
参数说明：-J 输出 JSON。
iperf3 -c 172.27.0.2 -t 3 -i 1 -J
{
"start": {
"connected": [{
"socket": 5,
"local_host": "172.27.0.3",
"local_port": 33986,
"remote_host": "172.27.0.2",
"remote_port": 5201
}],
"version": "iperf 3.9",
"system_info": "Linux 172.27.0.3 6.8.0-138-generic #138~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Aug 7 13:43:15 UTC x86_64",
"timestamp": {
"time": "Fri, 09 Oct 2026 04:28:53 GMT",
"timesecs": 1791520133
},
"connecting_to": {
"host": "172.27.0.2",
"port": 5201
},
"cookie": "2txgqlb43y5wa3wrs72uk5e3erwqehszx2ve",
"tcp_mss_default": 1448,
"sock_bufsize": 0,
"sndbuf_actual": 16384,
"rcvbuf_actual": 131072,
"test_start": {
"protocol": "TCP",
"num_streams": 1,
"blksize": 131072,
"omit": 0,
"duration": 3,
"bytes": 0,
"blocks": 0,
"reverse": 0,
"tos": 0
}
},
"intervals": [{
"streams": [{
"socket": 5,
"start": 0,
"end": 1.000113,
"seconds": 1.0001130104064941,
"bytes": 4321443840,
"bits_per_second": 34567644216.475548,
"retransmits": 114,
"snd_cwnd": 847080,
"rtt": 36,
"rttvar": 10,
"pmtu": 1500,
"omitted": false,
"sender": true
}],
"sum": {
"start": 0,
"end": 1.000113,
"seconds": 1.0001130104064941,
"bytes": 4321443840,
"bits_per_second": 34567644216.475548,
"retransmits": 114,
"omitted": false,
"sender": true
}
}],
"end": {
"streams": [{
"sender": {
"socket": 5,
"start": 0,
"end": 3.000123,
"seconds": 3.000123,
"bytes": 12592087040,
"bits_per_second": 33577522094.927444,
"retransmits": 114,
"max_snd_cwnd": 1051248,
"max_rtt": 58,
"min_rtt": 36,
"mean_rtt": 45,
"sender": true
},
"receiver": {
"socket": 5,
"start": 0,
"end": 3.040217,
"seconds": 3.000123,
"bytes": 12591300608,
"bits_per_second": 33132636540.089077,
"sender": true
}
}],
"sum_sent": {
"start": 0,
"end": 3.000123,
"seconds": 3.000123,
"bytes": 12592087040,
"bits_per_second": 33577522094.927444,
"retransmits": 114,
"sender": true
},
"sum_received": {
"start": 0,
"end": 3.040217,
"seconds": 3.040217,
"bytes": 12591300608,
"bits_per_second": 33132636540.089077,
"sender": true
},
"cpu_utilization_percent": {
"host_total": 95.373128613298235,
"host_user": 2.5201578883151745,
"host_system": 92.852938275066265,
"remote_total": 25.868867702630428,
"remote_user": 2.04338583066452,
"remote_system": 23.825471884205907
},
"sender_tcp_congestion": "cubic",
"receiver_tcp_congestion": "cubic"
}
}
解读：JSON 结构与文本输出一一对应。重点字段：start.connected[]（连接两端地址端口）、start.test_start（协议/流数/缓冲块大小/时长）、intervals[]（每个周期字节数与 bits_per_second）、end.streams[].sender（发送端汇总，含 max/mean_rtt）、end.sum_sent/sum_received（聚合吞吐）、end.cpu_utilization_percent（本端/对端 CPU 占用）。--get-server-output 可把服务端同样会执行的吞吐测试结果并入客户端 JSON 一并返回。
五、帮助输出
5.1 iperf3 --help（帮助全文，Ubuntu 22.04 / 3.9 版）
Usage: iperf3 [-s|-c host] [options]
iperf3 [-h|--help] [-v|--version]
Server or Client:
-p, --port # server port to listen on/connect to
-f, --format [kmgtKMGT] format to report: Kbits, Mbits, Gbits, Tbits
-i, --interval # seconds between periodic throughput reports
-F, --file name xmit/recv the specified file
-A, --affinity n/n,m set CPU affinity
-B, --bind <host> bind to the interface associated with the address <host>
-V, --verbose more detailed output
-J, --json output in JSON format
--logfile f send output to a log file
--forceflush force flushing output at every interval
--timestamps <format> emit a timestamp at the start of each output line
(using optional format string as per strftime(3))
-d, --debug emit debugging output
-v, --version show version information and quit
-h, --help show this message and quit
Server specific:
-s, --server run in server mode
-D, --daemon run the server as a daemon
-I, --pidfile file write PID file
-1, --one-off handle one client connection then exit
--server-bitrate-limit #[KMG][/#] server's total bit rate limit (default 0 = no limit)
(optional slash and number of secs interval for averaging
total data rate. Default is 5 seconds)
--rsa-private-key-path path to the RSA private key used to decrypt
authentication credentials
--authorized-users-path path to the configuration file containing user
credentials
--use-pkcs1-padding use pkcs1 padding at your own risk
Client specific:
-c, --client <host> run in client mode, connecting to <host>
--sctp use SCTP rather than TCP
-X, --xbind <name> bind SCTP association to links
--nstreams # number of SCTP streams
-u, --udp use UDP rather than TCP
--connect-timeout # timeout for control connection setup (ms)
-b, --bitrate #[KMG][/#] target bitrate in bits/sec (0 for unlimited)
(default 1 Mbit/sec for UDP, unlimited for TCP)
(optional slash and packet count for burst mode)
--pacing-timer #[KMG] set the timing for pacing, in microseconds (default 1000)
--fq-rate #[KMG] enable fair-queuing based socket pacing in
bits/sec (Linux only)
-t, --time # time in seconds to transmit for (default 10 secs)
-n, --bytes #[KMG] number of bytes to transmit (instead of -t)
-k, --blockcount #[KMG] number of blocks (packets) to transmit (instead of -t or -n)
-l, --length #[KMG] length of buffer to read or write
(default 128 KB for TCP, dynamic or 1460 for UDP)
--cport <port> bind to a specific client port (TCP and UDP, default: ephemeral port)
-P, --parallel # number of parallel client streams to run
-R, --reverse run in reverse mode (server sends, client receives)
--bidir run in bidirectional mode.
Client and server send and receive data.
-w, --window #[KMG] set window size / socket buffer size
-C, --congestion <algo> set TCP congestion control algorithm (Linux and FreeBSD only)
-M, --set-mss # set TCP/SCTP maximum segment size (MTU - 40 bytes)
-N, --no-delay set TCP/SCTP no delay, disabling Nagle's Algorithm
-4, --version4 only use IPv4
-6, --version6 only use IPv6
-S, --tos N set the IP type of service, 0-255.
The usual prefixes for octal and hex can be used,
i.e. 52, 064 and 0x34 all specify the same value.
--dscp N or --dscp val set the IP dscp value, either 0-63 or symbolic.
Numeric values can be specified in decimal,
octal and hex (see --tos above).
-L, --flowlabel N set the IPv6 flow label (only supported on Linux)
-Z, --zerocopy use a 'zero copy' method of sending data
-O, --omit N omit the first n seconds
-T, --title str prefix every output line with this string
--extra-data str data string to include in client and server JSON
--get-server-output get results from server
--udp-counters-64bit use 64-bit counters in UDP test packets
--repeating-payload use repeating pattern in payload, instead of
randomized payload (like in iperf2)
--username username for authentication
--rsa-public-key-path path to the RSA public key used to encrypt
authentication credentials
[KMG] indicates options that support a K/M/G suffix for kilo-, mega-, or giga-
iperf3 homepage at: https://software.es.net/iperf/
Report bugs to: https://github.com/esnet/iperf
5.2 版本信息 —— iperf3 -v
iperf 3.9 (cJSON 1.7.13)
Linux 172.27.0.3 6.8.0-138-generic #138~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Aug 7 13:43:15 UTC x86_64
Optional features available: CPU affinity setting, IPv6 flow label, SCTP, TCP congestion algorithm setting, sendfile / zerocopy, socket pacing, authentication
六、常见问题
6.1 连接被拒 / 无法连接
Q：客户端报 iperf3: error - unable to connect to server: Connection refused？
A：说明目标端口上没有服务端在监听。确认服务端已用 iperf3 -s（或 -p <port> 指定同端口）启动，且 -p、IP 一致；可用 ss -tlnp | grep 5201 在服务端核验监听状态。
6.2 -w 设置窗口报错
Q：iperf3 -w 1M 报 socket buffer size not set correctly？
A：请求的窗口值超过了系统套接字缓冲区上限（默认 net.core.wmem_max/rmem_max 约 212992）。可改用不超过上限的值（如 -w 200K）；确需大窗口先用 sysctl -w net.core.wmem_max=1048576 net.core.rmem_max=1048576 调高内核上限。
6.3 输出吞吐「虚高」
Q：内网测出来几十 Gbps，看起来不真实？
A：iperf3 测到的是路径当前能达到的吞吐。在同一内网段、共享转发路径且无瓶颈时，值偏高属正常；要得到贴近运营商的真实带宽，应在被测链路两端（网卡到网卡、跨交换机）对测，并结合多流 -P、UDP -u、反向 -R 交叉验证。
6.4 UDP 与 TCP 结果差异
Q：UDP 限 200M 很稳，TCP 却飙到 30G？
A：UDP 按 -b 限定的速率主动发包（UDP 默认 1 Mbit），是"先限速再测"；TCP 无 -b 时默认不限速（尽力而为），测的是链路能塞满的上限。两者用途不同：UDP 多用于抖动/丢包与实时业务模拟，TCP 用于带宽/吞吐基线。
七、参考链接
- iperf3 官方站点：https://software.es.net/iperf/
- 源码与 Issue：https://github.com/esnet/iperf
- man 手册页：iperf3(1)（
man 1 iperf3） - Ubuntu 软件包页面：https://packages.ubuntu.com/jammy/iperf3
- 本文素材来源：Ubuntu 22.04 双机实测（iperf3 3.9）
章节目录