If I want to use ROS2 to communicate different node in same pod on Kubernetes
i guess that to communicate different nodes in different container in the same pod.
Should I use Weave Net?
No, it is not necessary.
WeaveNet is one of the CNI(Container Network Interface) implementation.
you could use anything you want, also WeaveNet works fine.
at your point, Pod shares network interface and namespace, which means all of the containers( and any nodes in any containers) in the same pod can communicate with each other as localhost.
hope this helps, best