Flannel is a container networking interface implementation that provides a Kubernetes cluster network overlay. It functions as a layer 3 network fabric that assigns IP addresses to nodes and ensures connectivity for containers across a distributed cluster.
The project operates as a distributed subnet manager, utilizing a distributed data store to synchronize IPv4 address ranges and host metadata. It manages the allocation of unique subnet leases to individual hosts to prevent IP address conflicts across the network.
The system automates the setup of network interfaces and routing via the container network interface standard. It handles cross-host packet forwarding through a backend-agnostic approach, utilizing tunnels or cloud-native integrations to transport traffic between nodes.
