Testing traffic

  • Updated on Oct 16, 2026
  • 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, swx-tools, so users can test simple multicast traffic production/consumption. The tools run in a Docker container.

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

sudo ./install-groundswxtch.sh swx-tools

This installs the tools as a Docker container named swx-tools. If Docker is not installed, the installer tries to install it, unless --skip-docker-install is given. To install Docker manually, see How to Install Docker on RHEL and Ubuntu.

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 swx0-lan --sendto 239.1.1.1:5555 --pps 1000 --seconds 30
sudo docker exec swx-tools swx-perf consumer --nic swx0-lan --recvfrom 239.1.1.1:5555 --seconds 30 --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 and the consumer stop on their own.

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

To run swx-perf from an interactive bash shell inside the container:

sudo docker exec -it swx-tools bash

Choosing the network interface

The single most common cause of "0 packets" is the wrong --nic. At the end of the swx-tools install, the installer prints interface hints; on a VM that also runs groundSwXtch, follow the note below.

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 swx0-lan (gswx-lan on earlier builds). 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: sudo docker exec swx-tools pkill -INT -f swx-perf.