Cilium
also: eBPF CNI, Cilium project
Cilium is an open-source networking and security project that uses eBPF (extended Berkeley Packet Filter) to provide network connectivity, load balancing, and security policies for containers and Kubernetes clusters.
Cilium operates at the kernel level using eBPF, a powerful in-kernel virtual machine that can run sandboxed programs without modifying kernel source code. This allows Cilium to enforce network policies, perform observability, and manage traffic with minimal overhead compared to traditional userspace networking tools.
In Kubernetes environments, Cilium serves as a Container Network Interface (CNI) plugin, managing pod-to-pod communication and implementing network segmentation. For example, you can define a policy that only allows pods with label app=frontend to communicate with pods labeled app=backend, and Cilium enforces this at the kernel level.
Beyond networking, Cilium provides API-aware security policies (understanding HTTP, gRPC, Kafka), load balancing, and deep visibility into network traffic through eBPF-based monitoring, making it valuable for both network management and security compliance in cloud-native environments.