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Testing traffic

  • Published on Jul 24, 2026
  • 2 minute(s) read
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WHAT TO EXPECT

In this article, users will learn how to test simple multicast traffic creation/consumption using provided tools.

Provided tools

groundSwXtch provides a set of tools so users can test simple multicast traffic production/consumption. The tools are in a Docker container. Users should check How to Install Docker on RHEL and Ubuntu.

To help test the groundSwXtch, swx tools can be installed on the groundSwXtch or any other VM using this command:

sudo ./install-groundswxtch.sh tools

This installs the tools as a Docker container.  To run the tools, Docker is needed in the commands; see examples below:

sudo docker exec swx-tools swx-perf producer --nic enp0s5 --sendto 239.1.1.1:5555 --pps 1000 --seconds 30
sudo docker exec swx-tools swx-perf consumer --nic enp0s5 --recvfrom 239.1.1.1:5555

You can also log into an interactive bash shell in the container and execute the swx-perf command directly, by doing the following:

docker exec -it swx-tools bash

Running swx-perf

swx-perf has two roles: a producer that sends multicast traffic and a consumer that receives it. Run them through docker exec:

sudo docker exec swx-tools swx-perf producer --nic gswx-lan --sendto 239.1.1.1:5555 --pps 1000 --seconds 30
sudo docker exec swx-tools swx-perf consumer --nic gswx-lan --recvfrom 239.1.1.1:5555 --json-report

The key flags:

  • --nic — the interface to send on or receive from (see the note below on which one to use).

  • --sendto / --recvfrom — the multicast group and port (group:port).

  • --pps — packets per second for the producer.

  • --seconds — how long the run lasts. Always set this so the producer self-terminates.

  • --json-report — prints a structured packet and loss summary at the end of the run.

You can also log into an interactive bash shell in the container and run swx-perf directly:

docker exec -it swx-tools bash

For the full list of swx tools, refer to Tools and Testing.

Choosing the network interface

The single most common cause of "0 packets" is the wrong --nic. The installer prints the suggested interface at the end of the install.

PLEASE NOTE

If the user is running the tools in a VM that's also running groundSwXtch, the network interface must be the virtual interface gswx-lan. Only when generating traffic from a separate machine should the physical NIC (for example, enp0s5) be used.

Changing the LAN device between a virtual and a physical interface flushes the multicast subscriptions — they must be re-added afterward.

Notes

  • Ports must be 1024 or higher. Avoid 5000 and 6000 (reserved by spp) and 9999 (reserved by the swxtch ecosystem); 5555 is a safe choice.

  • A docker exec started without -it does not forward Ctrl+C to swx-perf inside the container, so the producer keeps running as an orphan. Always bound the run with --seconds, or use docker exec -it. To stop a stray producer: docker exec swx-tools pkill -INT -f swx-perf.

  • The swx-tools image is published for linux/amd64 only.

Now the swx-tools can be run as normal; for swx-tools commands, refer to Tools and Testing.

PLEASE NOTE

If the user is using the tools in a VM that’s running groundSwXtch, the network interface must be the virtual interface gswx-lan.