IPsec and Network Security - 2026 TRex Testing (Frankfurt, 10-12 Feb)

2026 TRex Testing (Frankfurt, 10-12 Feb)

Overview

This guide provides a quick start for installing and testing TRex (Cisco's Traffic Generator) on Ubuntu 24.04 (Noble Numbat) LTS

Prerequisites

Before installing TRex, ensure your system meets the following requirements:

Operating System: Ubuntu 24.04 LTS
Python: Python 3.12 (TRex v3.08 is tied to this version)
CPU: Multi-core processor with NICs bound to the cores you are using
Network: Tested with Mellanox ConnectX-5 or ConnectX-7
DOCA-OFED: Must match your OS distribution — https://developer.nvidia.com/networking/doca

Installation

Installing Python 3.12

TRex v3.08 (current as of Feb 2026) requires Python 3.12, which is older than what ships with Ubuntu 24.04.

Download the Python 3.12 source tarball:

wget https://www.python.org/ftp/python/3.12.9/Python-3.12.9.tgz

Extract it, run configure, and install.

tar -zxf Python-3.12.9.tgz
cd Python-3.12.9
./configure --enable-optimizations
make -j 3 install

To always use Python 3.12 with TRex, create a virtual environment (one-time setup). After that, activate this venv every time you work with TRex.

Run this from /root or another persistent location:

apt install python3.12-venv
python3.12 -m venv venv

Activating the Python 3.12 venv

Each time you log in to work with TRex, activate the venv first:

source /root/venv/bin/activate
# To verify:
type python3.12 # it should show /root/venv/bin/python3.12

Installing DOCA-OFED

For setups using Mellanox ConnectX NICs, DOCA-OFED is required to ensure proper driver and DPDK support. Configuration details are provided at the end of this document.

Navigate to the DOCA downloads page and select the local package for your OS.

wget https://www.mellanox.com/downloads/DOCA/DOCA_v3.2.1/host/doca-host_3.2.1-044000-25.10-ubuntu2404_amd64.deb
dpkg -i doca-host_3.2.1-044000-25.10-ubuntu2404_amd64.deb
apt-get update
apt-get -y install doca-ofed
dkms autoinstall
mst start
mst status -v

Installing TRex 3.08

wget --no-check-certificate --no-cache https://trex-tgn.cisco.com/trex/release/latest
mv latest trex-v3.08.tgz
tar xvf trex-v3.08.tgz
mv v3.08 /var/tmp/trex-v3.08  # you may need to chmod 777 first
cd /var/tmp/trex-v3.08/
rm  so/x86_64/libstdc++.so.6
sysctl -w vm.nr_hugepages=2048  # add this to /etc/sysctl.d to make it permanent.
chmod -R 777 /var/tmp/trex-v3.08/

At the time of writing, latest pointed to v3.08.

Starting TRex Server

TRex is installed under /var/tmp/trex-v3.08 on the sunset host. The server runs in the foreground, so start it inside a screen session — that way you can reattach later with screen -x to check its output.

Activate the venv first, then launch screen and start TRex inside it:

source /root/venv/bin/activate
screen bash
sysctl -w vm.nr_hugepages=2048
cd /var/tmp/trex-v3.08
./t-rex-64 -i --no-scapy --cfg /etc/trex_cfg.yaml -c 8

The server takes a few seconds to initialize.

Running a TRex Test Script

From a second terminal (also inside the Python 3.12 venv), run one of the test scripts. For example:

git clone https://github.com/antonyantony/ietf-123-pcpu"

cd ietf-123-pcpu/tests-trex
./u1.py

or

./u1.py --src-ip 192.0.1.253 --dst-ip 192.0.2.253 --pps 1M --frame-size 1518 --flows 2 --duration 10 --flows-end 2 --runs 2

The script use u1.conf as configuration file, to generate a config template, the TRex server should not be when generating config, otherwise gen-config won't be able to detect nexthop ARP/neighbor MAC address which is used in dst-mac. If the dst-mac or rev-dst-mac address is incorrect the traffic will be dropped with NO ERRROR counters.

./u1.py --gen-config

Check the the src/dst, MAC addresses are correct.

u1.py is a simple UDP sender/receiver that measures throughput and packet loss. It stores results in JSON, which are later processed with Pandas and plotted using Matplotlib.

Appendix A: Mellanox DOCA-OFED Diagnostics

This section is only needed if you are troubleshooting your Mellanox NIC setup. If TRex starts and traffic flows, you can skip this.

After installing DOCA-OFED, run mst start once. To verify that your NICs are detected, check the output of mst status -v:

 mst status -v
MST modules:
------------
    MST PCI module is not loaded
    MST PCI configuration module loaded
    -E- Unknown argument "--v"
root@sunset:~/ietf-123-pcpu/tests-trex# mst status -v
MST modules:
------------
    MST PCI module is not loaded
    MST PCI configuration module loaded
PCI devices:
------------
DEVICE_TYPE             MST                           PCI       RDMA                                               NET                                     NUMA
ConnectX5(rev:0)        /dev/mst/mt4121_pciconf0.1    01:00.1   mlx5_1          net-redwest                             0

ConnectX5(rev:0)        /dev/mst/mt4121_pciconf0      01:00.0   mlx5_0          net-redeast                             0

Appendix B: TRex scapy permission issue

./t-rex-64 -i -c 4 --cfg /etc/trex_cfg.yaml

    Error: current path is not readable by user "nobody" (starting at /root).
    Two possible solutions:

    1. (Recommended)
        Copy TRex to some public location (/tmp or /scratch, assuming it has proper permissions (chmod 777 etc.))

    2. (Not recommended)
        Change permissions of current path. (Starting from directory /root).
        chmod 777 /root -R

Could not start scapy daemon server, which is needed by GUI to create packets.
If you don't need it, use --no-scapy-server flag.
ERROR encountered while configuring TRex system

Appendix C: TRex v3.08 MTU setting

Trex v3.08 seems to need larger mtu set on Mellanox CX cards. The OFED/DPDK should newer than 25.07.

./t-rex-64 -i --no-scapy
The ports are bound/configured.
Starting  TRex v3.08 please wait  ...
 set driver name net_mlx5
 driver capability  : TCP_UDP_OFFLOAD  TSO  LRO
 set dpdk queues mode to DROP_QUE_FILTER
 Number of ports found: 2
zmq publisher at: tcp://*:4500
mlx5_net: port 0 failed to set MTU to 65518
ETHDEV: Port0 dev_configure = -22
EAL: Error - exiting with code: 1
Cannot configure device: err=-22, port=0

ofed_info -s
OFED-internal-25.10-1.7.1:

workaround: port_mtu: 9000

Appendix D: Trex Config file

cat /etc/trex_cfg.yaml

- version         : 2
  port_limit      : 2
  interfaces:       ["02:00.0", "02:00.1"]

  platform:
    master_thread_id: 0
    latency_thread_id: 1
    dual_if:
      - socket: 0
        threads: [2,3,4,5,6,7]

  port_info       :  # Port IPs.
          - ip         : 192.0.1.250
            default_gw : 192.0.1.254
          - ip         : 192.0.2.250
            default_gw : 192.0.2.254
  port_mtu: 9000

Appendix E: Trex with scapy

pip install scapy This may give you permission issues.

pip install scapy
Collecting scapy
  Downloading scapy-2.7.0-py3-none-any.whl.metadata (5.8 kB)
Downloading scapy-2.7.0-py3-none-any.whl (2.6 MB)
   ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 2.6/2.6 MB 19.1 MB/s eta 0:00:00
Installing collected packages: scapy
Successfully installed scapy-2.7.0
(venv-3.12-202260217) root@sun:/var/tmp/trex-v3.08# ./t-rex-64 -i
Starting Scapy server... Scapy server failed to run
Output: b'taskset: failed to execute /root/venv/bin/python3: Permission denied\n'
Could not start scapy daemon server, which is needed by GUI to create packets.
If you don't need it, use --no-scapy-server flag.
ERROR encountered while configuring TRex system

chmod 755 /root/venv/bin/python3
chmod 755 /root/venv/bin/python3.12
chmod 755 /root/venv/bin/python3
chmod 755 /root/venv/bin/python3.12