The kubelet service configuration has an option for which CNI network plugin to use.
--network-plugin=cni This tells the kubelet to use a CNI plugin. The plugins are typically stored in /opt/cni/bin but this can be configured with the --cni-bin-dir=/opt/cni/bin option.
This folder contains all of the currently installed networking plugin binaries.
The config file(s) for which CNI plugin to use are stored in /etc/cni/net.d but this can be configured with the kubelet option --cni-conf-dir=/etc/cni/net.d.
If there is more than one config file then they are loaded in alphabetical order with the first being the default.