TRex

TRex is an open-source traffic generator for benchmarking network platforms with realistic traffic. It best suits network engineers and teams that need scalable traffic generation and protocol emulation on Linux infrastructure. Its broad traffic modes and Python automation make it a capable free option, though hardware requirements and virtual-environment limits shape where it fits.

Overview

TRex generates Layer 3–7 traffic in stateless, stateful, and advanced stateful modes. Stateless workloads can use multiple streams, alter packet fields, and collect per-stream or per-group statistics, latency, and jitter. Advanced stateful mode emulates Layer 7 traffic over scalable TCP and UDP flows. The site says one server can scale up to 200 Gb/sec, making TRex relevant to high-volume benchmarks as well as switch, routing, client/server scale, production, and DDoS traffic tests.

Its protocol emulation covers ARP, IPv6, neighbor discovery, MLD, IGMP, ICMP, DOT1X, DHCPv4 and DHCPv6, and DNS. The broader protocol support also includes LLDP, mDNS, NetFlow/IPFIX, OSPF, RIP, and GTP-U. Python APIs span its traffic-generation, emulation, and NDR functions; stateless automation can also use JSON-RPC, and a console interface is provided. BIRD integration supports Linux-based stack configuration.

That range favors teams building repeatable network-device benchmarks or automated test workflows. It is less suitable when accurate latency measurement in a virtual machine is essential: virtual switches can constrain throughput to around 1 MPPS, and VM latency results are not accurate.

Key features

Traffic generation and emulation

Stateless mode gives users fine-grained stream and packet-field control alongside latency, jitter, and statistics. Stateful and advanced stateful modes add scalable TCP/UDP workloads and Layer 7 emulation, which is useful when a benchmark needs more than packet-rate generation. Emulated network protocols extend the range of device and stack scenarios TRex can represent.

Automation and deployment

Python APIs cover the main TRex functions, while JSON-RPC offers a route to stateless control from other languages that support it. The documentation describes VM and Docker deployments for lower-performance, low-footprint use without extra hardware. Those environments trade convenience for meaningful performance constraints; they should not stand in for hardware when throughput or latency accuracy matters.

Pricing

TRex costs nothing. Its open-source Linux application is free of charge, with hardware and NIC requirements applying. There are no paid tiers or seat and usage quotas stated for TRex, so it is a strong fit for teams able to supply and manage compatible infrastructure rather than pay for a hosted service. The free price does not remove the cost or effort of suitable hardware and deployment.

Platforms

TRex is a Linux application built on DPDK and Linux kernel modules, and is described as working on COTS x86 servers. ARM compilation is possible, but ARM is not tested in its regression. Although the platform listing also includes API, macOS, self-hosted, web, and Windows, its core application is Linux-based. TRexViewer live monitoring is supported only on Windows.

Who it's for

TRex is a good match for network teams benchmarking devices at scale, generating traffic for switch or routing tests, emulating clients and servers, or automating repeatable network tests. It also suits engineers who can operate Linux and meet hardware and NIC requirements. Choose a different approach if you need dependable VM latency results, tested ARM support, or a tool that avoids infrastructure management.

Pros and cons

• Pros: Three traffic-generation modes cover stateless workloads through scalable Layer 7 TCP/UDP emulation, supporting varied benchmark needs.
• Pros: Python automation and JSON-RPC stateless control enable integration into test workflows without limiting users to the console.
• Pros: Open-source access costs nothing, with no paid TRex tier to unlock its core capabilities.
• Cons: Hardware and NIC requirements make deployment a poor fit for teams seeking an infrastructure-free service.
• Cons: Virtual switches can cap throughput around 1 MPPS, and VM latency results are inaccurate, so virtual deployments are not substitutes for performance-grade testing.
• Cons: ARM compilation is possible but not regression-tested, and the TRexViewer monitoring application is Windows-only.

Alternatives

For more network-testing options, browse Network Testing Software.

• PingPlotter is worth considering for connection monitoring across iOS, Linux, macOS, web, and Windows; its free plan is limited to one connection, no remote collection, and 10-minute monitoring history, while Professional Edition is $29 a month.
• Invariant is an API- and web-based alternative with a free Basic account described as having effectively no usage limits.
• Cisco pyATS is another free, open-source choice for Linux, macOS, and self-hosted environments.
• perfSONAR is a free, open-source network measurement toolkit for Linux and self-hosted use, with installation and operation requiring user-managed infrastructure.
• EVE-NG may suit users seeking a network emulation environment; its free plan permits 7 nodes per instance and 63 per lab, with Admin role only.
• NetBeez is a paid option with Starter, Base, and Enterprise plans for network or remote-worker agents.
• IP Fabric is a paid alternative with an annual subscription based on active devices and cloud objects, plus a support package; a free trial is offered.
• GNS3 is free, open-source software for users who want a downloadable network simulation tool.

Verdict

Choose TRex if your team needs flexible, automatable traffic generation for serious network benchmarks and can provide Linux-compatible hardware and NICs. Its breadth of traffic modes and protocol emulation is the central draw at no software charge. Look elsewhere if virtualized latency accuracy, tested ARM support, or a managed deployment matters more than that control.