iPerf2

iPerf2 is a free, self-hosted network performance tool for operators, developers, and labs that can run endpoints at both ends of a link. It is a strong choice when you need deliberately shaped TCP or UDP traffic and measurements beyond simple speed, while its socket-level scope and separation from iPerf3 require careful tool selection.

Overview

Every test uses a server to receive traffic and a client to generate and send it. That active, two-ended model suits teams with control of hosts, test appliances, or lab networks; it is not a convenient substitute for a one-click internet speed test. You can examine throughput, latency, link capacity, and responsiveness under traffic conditions you define, making the results useful for diagnostics and capacity work.

iPerf2 is free and self-hosted, with ticket and discussion pages on SourceForge for project support. The project manual also describes an Android client with live meters for throughput, latency, and congestion signals, useful when a mobile endpoint is part of the test.

Key features

Traffic patterns and protocols

TCP and UDP tests can run unidirectionally, bidirectionally, full-duplex, or as simultaneous multi-stream traffic. This range lets an engineer separate outbound behavior from return-path behavior, observe competing flows, and model a more demanding exchange. UDP L4S support is part of the professional feature set. IPv4, IPv6, and multicast are supported, including source-specific multicast joins, giving it a broader scope than a basic point-to-point throughput check.

Measurements and reporting

Supported measurements include one-way delay, round-trip time, jitter, packet loss, and throughput. Reports can include enhanced metrics and can be written in CSV, which is practical for retaining runs or processing them in another system. The important boundary is that metrics are taken at socket-level reads and writes; lower-level protocol-header overhead is outside the readings. Use the results to compare application-visible transfer behavior, not as a complete wire-level accounting.

Access controls

Permit-key authentication uses a timestamped HMAC-SHA256 value, with replay limited by a configurable time window. The professional feature set adds server access gating and remotely enabled server-side latency histograms. Its source is freely available to inspect and build, so teams can keep a compile-time feature set under their own control rather than depending on a hosted service.

Compatibility boundary

iPerf2 and iPerf3 are independent implementations and do not interoperate. That is a deployment constraint: endpoints must use the same implementation, and an existing iPerf3 estate cannot simply be mixed into an iPerf2 test.

Pricing

Both editions are free, with no seat, quota, trial, or renewal terms stated. Community edition covers the core traffic tests and network families. Choose Professional when authenticated server access, remotely enabled histograms, or UDP L4S matters; otherwise its additional controls do not change the need to operate your own client and server.

Platforms

iPerf2 runs on Android, Linux, macOS, and Windows, and is available for self-hosted deployment. The cross-platform choices help place endpoints on different operating systems, while the self-hosted model leaves installation and endpoint administration to you.

Who it's for

Network operators can use its directional, duplex, multicast, and loss or jitter measurements to investigate links under controlled load. Developers and QA teams gain CSV-capable output and configurable stream patterns for repeatable checks. It also fits training and lab environments that need IPv4 and IPv6 coverage. It is a weaker fit for users who want hosted monitoring, passive observation, or interoperability with iPerf3, and for anyone unable to run both test endpoints.

Pros and cons

Pros

• Broad active test design: TCP and UDP, multiple directions, full duplex, and multi-stream modes expose behavior under varied loads.
• Rich network coverage: IPv4, IPv6, multicast, and source-specific multicast joins support more than a basic unicast check.
• Useful diagnostics: Delay, round-trip time, jitter, packet loss, throughput, enhanced metrics, and CSV output support analysis and record keeping.
• Free control features: Permit-key authentication, server gating, and latency histograms are included in the free Professional edition.

Cons

• Endpoint administration required: A server and client must be available for every test, which adds operational work.
• Socket-level scope: Results omit lower-level protocol-header overhead and should not be treated as wire-level totals.
• No iPerf3 interoperability: Existing iPerf3 endpoints cannot participate in an iPerf2 test.

Alternatives

OpenSpeedTest is the better pick for a free HTML5 speed test, web deployment, or an embeddable widget, with Android, iOS, desktop, and self-hosted options.

LibreSpeed suits readers wanting a self-hosted, free and open-source speed test rather than iPerf2's configurable traffic diagnostics.

PingPlotter is preferable for ongoing path monitoring; its free plan allows one connection and 10 minutes of history, while Professional Edition costs $29 a month.

TRex is an open-source Linux traffic generator when its hardware and NIC requirements fit the deployment.

EVE-NG is a network-emulation environment, with a free tier capped at 7 nodes per instance and 63 nodes per lab.

GNS3 is free, open-source network software for building virtualized network topologies rather than measuring a live link directly.

Mininet is suited to Linux-based network emulation, limited by one server's CPU and bandwidth.

Netperf is a free MIT-licensed benchmark when its configurable platform and test requirements match your setup.

See the Network Testing Software directory for more options.

Verdict

Choose iPerf2 if you can run both endpoints and need free, actively generated TCP or UDP tests with multicast, IPv4/IPv6 coverage, and detailed delay, loss, jitter, and throughput measures. Look elsewhere if you need hosted or passive monitoring, wire-level accounting, or an endpoint that interoperates with iPerf3.