ROS2: How to confirm that a DEFAULT_FASTRTPS_PROFILES.xml have been loaded and are used?

edit

The XML file should be named DEFAULT_FASTRTPS_PROFILES.xml (drop LTE_ from the front) and it must be located in the pwd directory where you ros2 run your application. Example file:

<?xml version="1.0" encoding="UTF-8" ?> 
<profiles> 
    <participant profile_name="participant_profile" is_default_profile="true"> 
        <rtps> 
            <builtin> 
                <metatrafficUnicastLocatorList> 
                    <locator/> 
                </metatrafficUnicastLocatorList> 
                <initialPeersList> 
                    <locator> 
                        <address>192.168.1.111</address> 
                    </locator> 
                </initialPeersList> 
            </builtin> 
        </rtps> 
    </participant> 
</profiles>

In one terminal run sudo tcpdump -v | grep "192.168.100.111", and in a second terminal (in the same directory) start a ros2 node, e.g. ros2 run demo_nodes_cpp talker. At minimum, you should see an ARP request like this:

14:09:06.148381 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.111 tell 192.168.100.182, length 28

To convince yourself that DEFAULT_FASTRTPS_PROFILES.xml is being loaded, changed the IP address to a non-existent host and confirm the ARP request.