gazebo sim: Exception sending a multicast message:Network is unreachable

[MMarcus95]

Error happening sometimes when launching the simulation or while simulating. Need further investigation
related issue: gazebosim/gz-sim#1879
fix (not work when unplugging cable): https://docs.ros.org/en/rolling/How-To-Guides/Installation-Troubleshooting.html#enable-multicast

[MMarcus95]

Seems related to gazebo transport.

FIXED ONCE SETTING THIS ENV VARIABLE

export GZ_IP=127.0.0.1

added this export in the wiki