Cisco pyATS vs TRex

Cisco pyATS is a Python framework for network testing, automation, and validation, available free under the Apache 2.0 license. It supports sanity, feature, solution, system, and scale test and verification workflows, with reusable data-driven tests ranging from simple checks to complex asynchronous suites. Genie libraries provide device connectivity, parsers, APIs, platform-agnostic feature models, reusable test cases, and a YAML-driven test runner. Built-in device libraries cover Cisco IOS, IOS XE, IOS XR, NX-OS, and ASA; plugins and extensions can add other platforms. Connections can use CLI, NETCONF, or RESTCONF. XPRESSO manages test suites, environments, testbeds, resources, live test views, and archived results with comparisons and analytics. It supports on-demand, bundled, and scheduled runs through Jenkins and Docker backends. Cisco also documents Ansible community integrations and out-of-the-box RobotFramework support. pyATS runs on Linux and macOS and supports self-hosted deployment. Cisco says more than 75% of its codebase is open source on GitHub. Email support is best-effort and usually receives a reply within a day.

TRex is an open source traffic generator for benchmarking platforms with realistic network traffic. It produces Layer 3–7 traffic in stateless, stateful, and advanced stateful modes. Stateless mode supports multiple streams, packet-field changes, and per-stream or per-group statistics, latency, and jitter. Advanced stateful mode emulates Layer 7 traffic over scalable TCP and UDP flows. Emulation includes ARP, IPv6, ND, MLD, IGMP, ICMP, DOT1X, DHCPv4, DHCPv6, and DNS. TRex offers Python automation APIs and a console interface; stateless functions can also be used through JSON-RPC. The manual describes it as a Linux application using DPDK and Linux kernel modules, intended for COTS x86 servers. The site says one server can scale up to 200 Gb/sec. It can run in a virtual machine or Docker for low-performance, low-footprint use, but virtual switches can limit throughput and virtual-machine latency results are not accurate. TRex is free, with hardware and NIC requirements. The GUI monitoring application TRexViewer is supported only on Windows.