Bad network performance with multiple robots in ROS2

[Krzo99]

Hello,

I'm using ROS2 with FastDDS. With one robot (and the PC), the network works well, without any problems.
However, as soon as I add another robot, running the same software as the first, the network grinds to a halt, 90% of the time.
This means, msgs not being received on the PC, or being 10s-15s late. There isn't any topic name collisions, as the same setup works the other 10% of the time.

Each robot has hundreds of topics, publishers & subscribers on ~10 nodes. My theory is, that the network gets overwhelmed with all the multicasting, and grinds the network to a halt, creating a multicast storm. Sometimes the router even crashes/reboots.

Would it be possible to configure fastdds_config.xml file, to disable multicasting, if I know all the IP addresses of the robots & PC.
Could you provide the example, I'm a bit lost,
PCs IP is 192.168.1.123, robot's IP is: 192.168.1.111

Thank you for all the help!