Connectivity Test - Which IP type has the CGNAT issue?

General
1

I’m using ROS 2 with Fast DDS Discovery Server over Husarnet and facing an issue with topic discovery.

Setup

Computer A (Host / Discovery Server):

  • Runs the Fast DDS Discovery Server on the husarnet-local interface and port 11811

  • Environment variables:

    • RMW_IMPLEMENTATION=rmw_fastrtps_cpp
    • ROS_SUPER_CLIENT=TRUE
    • ROS_DISCOVERY_SERVER=ds-host:11811

  • Has an IP address in the 172.x.x.x range

Computer B (Client):

  • Uses the same environment variables
  • Also uses ds-host as the discovery server
  • Has an IP address in the 192.x.x.x range

Issue:

When running ros2 topic list on both machines, I only see topics associated with 172.x.x.x IPs. Topics over the Husarnet 192.x.x.x IPs are not visible.
The Husarnet troubleshooting guide mentions this may be due to one of the machines being behind CGNAT.

Question:

Given that Computer A (the host) has a 172.x.x.x IP and Computer B (the client) has a 192.x.x.x IP, which computer is more likely behind CGNAT and causing this issue?
How can I verify this and resolve the topic discovery problem?

2

If I were to guess this may not be a CGNAT issue - we’ve seen similar issues when both networks were sharing an internet connection while being behind an oddly specific firewall setups. Please try this from two separate location (which will be more similar to the Competition environment) or, i.e. using a GSM hotspot (which will introduce CGNAT and tunelling, but may enable you to figure out whether FastDDS or Husarnet is at fault)