TRex

TRex is a free, open-source traffic generator for benchmarking network platforms with realistic traffic. It is best suited to network engineers who need scalable traffic workloads, protocol emulation, and automation on Linux-based infrastructure. Its breadth is a strong fit for demanding device tests, but hardware requirements and virtual-environment limits narrow where it can deliver useful results.

Overview

TRex generates Layer 3–7 traffic in stateless, stateful, and advanced stateful modes. Stateless workloads can span multiple streams, change 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 a strong candidate for high-scale benchmarks as well as switch, routing, client/server scale, production, and DDoS traffic tests.

Its emulation includes ARP, IPv6, neighbor discovery, MLD, IGMP, ICMP, DOT1X, DHCPv4, DHCPv6, and DNS. Broader protocol support includes LLDP, mDNS, NetFlow/IPFIX, OSPF, RIP, and GTP-U. That range helps teams reproduce varied network conditions rather than relying only on basic throughput traffic.

Key features

Automation is a practical strength. Python APIs cover stateless, stateful, advanced stateful, emulation, and NDR functions; the stateless API can also be used through JSON-RPC from compatible languages. A console interface is provided, and BIRD integration supports Linux-based stack configuration. These options suit teams that need repeatable tests integrated into their own workflows.

There are important deployment constraints. The manual describes TRex as a Linux application using DPDK and Linux kernel modules, intended to work on COTS x86 servers. ARM compilation is possible, but ARM is not tested in the regression. Running it in a virtual machine or Docker can provide a lower-performance, lower-footprint setup without extra hardware, but virtual switches can limit throughput to around 1 MPPS, and virtual-machine latency results are not accurate. That makes virtualization useful for lightweight exploration, not a substitute for reliable performance or latency measurement.

TRexViewer, the live monitoring application, is supported only on Windows. Support resources include the TRex community forum and Cisco DevNet community. The official pages make no security certification or compliance claims.

Pricing

TRex is free and open source. The TRex plan costs nothing and includes an open-source Linux application; hardware and NIC requirements apply. There are no paid tiers to trade features against, so it suits teams able to supply and configure appropriate Linux hardware. Those who need low-footprint use can run it in a virtual machine or Docker, but should accept the stated performance and latency limits.

Platforms

TRex is a Linux application, despite its API, web, macOS, and Windows platform labels. The Windows-only TRexViewer provides live monitoring, while the core traffic generator depends on Linux, DPDK, and compatible hardware. Teams choosing deployment should plan around that distinction rather than expect a native macOS or Windows traffic-generation application.

Who it's for

TRex is a good match for network engineering teams benchmarking high-scale stateful devices, generating DDoS traffic, testing switches, scaling clients and servers, validating production traffic, or exercising routing protocols. Its multiple traffic modes, protocol coverage, and automation interfaces make it particularly useful where tests need to be varied and repeatable. It is a poor fit for users seeking accurate virtual-machine latency measurements or a lightweight desktop tool that avoids Linux and NIC requirements.

Pros and cons

• Broad traffic coverage: Stateless, stateful, and advanced stateful modes support workloads from packet-level streams to scalable Layer 7 TCP and UDP flows.
• Useful automation options: Python APIs, JSON-RPC for stateless use, and a console interface support scripted and repeatable testing.
• High stated scale: The site says a single server can reach 200 Gb/sec, which is relevant to high-volume platform benchmarks.
• Hardware and operating-system demands: The Linux, DPDK, and NIC requirements make setup less suitable for teams without compatible infrastructure.
• Virtual test limits: Virtual switches can constrain throughput to around 1 MPPS, and virtual-machine latency results are inaccurate.
• Limited viewer platform: TRexViewer live monitoring is supported only on Windows.

Alternatives

For a wider comparison, see Network Testing Software. Choose OpenSpeedTest instead for a free HTML5 network speed test with an embed widget for personal and commercial use, rather than TRex's scalable traffic-generation and emulation focus. LibreSpeed is another free, self-hosted option if a simpler open-source speed test is the goal.

PingPlotter may suit readers looking for connection monitoring: its free plan is limited to one connection, no remote collection, and 10-minute monitoring history. Choose EVE-NG when a network lab is the priority; its free plan allows 7 nodes per instance and 63 nodes per lab. GNS3 is a free, open-source alternative for users who want network simulation rather than traffic generation.

iPerf2 is another free network testing tool, with a compile-time feature set and permit-key access gating in its professional edition. Mininet is a better fit for Linux-kernel-based network emulation, though it is limited by one server's CPU and bandwidth. Netperf offers free source-code distribution under an MIT license for readers who want a configurable performance-testing tool.

Verdict

Choose TRex if you need a free, scalable generator for realistic network-device benchmarks, with protocol emulation and automation broad enough for varied test workflows. Its strongest case is the combination of traffic modes, high stated scale, and programmable control. Look elsewhere if your work depends on accurate latency in a virtual environment or if Linux, DPDK, and suitable NICs are outside your setup.