Container Networking Solutions

Container networking is how containers get network interfaces and IP addresses, find each other, and reach external networks. In Kubernetes it is implemented by a Container Network Interface (CNI) plugin, often combined with network policy, ingress and service-mesh components.

A CNI plugin provides pod-level connectivity and network policy at layers 3 and 4. A service mesh such as Istio or Linkerd adds service-to-service features like mutual TLS, retries and traffic observability, typically at layer 7, on top of that connectivity.

It depends on scale and requirements. Flannel suits simple clusters, Calico and Cilium add network policy and, in Cilium's case, eBPF-based performance and observability, and Multus helps when pods need several network interfaces. Enterprise vendors add support, multi-cloud connectivity and integrated security.

eBPF lets networking, observability and security logic run safely inside the Linux kernel. CNI plugins such as Cilium use it to replace iptables-based kube-proxy, giving faster service load balancing, network policy enforcement and flow visibility with less overhead at scale.

Network policies control which pods may talk to each other and are enforced by the CNI plugin. Ingress controllers and the Gateway API manage traffic entering the cluster, and load balancers such as MetalLB provide external IPs on bare metal. Most clusters combine all three.