> For the complete documentation index, see [llms.txt](https://atomoh.gitbook.io/kubernetes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://atomoh.gitbook.io/kubernetes/en/networking/cilium/glossary.md). # Glossary > **Last Updated**: February 22, 2026 This document provides explanations of key terms and abbreviations related to Cilium. This glossary helps in understanding Cilium, eBPF, Kubernetes, and networking concepts. ## Term Categories Terms are classified into the following categories: * Blue **Cilium-related terms** * Orange **eBPF-related terms** * Green **Kubernetes-related terms** * Purple **Networking-related terms** * White **General terms** ## A **API (Application Programming Interface)** - General * A set of interface definitions that enable communication between applications **AWS ENI (Elastic Network Interface)** - Networking * Virtual network interface provided by Amazon Web Services * Used in Cilium's AWS ENI IPAM mode **ARP (Address Resolution Protocol)** - Networking * Protocol that converts IP addresses to MAC addresses * Essential protocol for communication in L2 networks ## B **BGP (Border Gateway Protocol)** - Networking * Standard external gateway protocol used to exchange routing information on the Internet * Can be used as native routing mode in Cilium **BPF (Berkeley Packet Filter)** - eBPF * Technology for packet filtering, predecessor to eBPF * Originally developed for network packet capture **BPF Maps** - eBPF * Key-value stores used to store and retrieve data in eBPF programs * Used for data sharing between user space and kernel space ## C **CGroup (Control Group)** - Kubernetes * Linux kernel feature that limits and isolates resource usage of process groups * Used for container resource limiting **CIDR (Classless Inter-Domain Routing)** - Networking * Method for IP address allocation and routing aggregation * Example: 192.168.1.0/24 represents IP address range from 192.168.1.0 to 192.168.1.255 **CNI (Container Network Interface)** - Kubernetes * Standard interface between container runtimes and network plugins * Cilium is one of the CNI implementations **CoreDNS** - Kubernetes * DNS server commonly used in Kubernetes clusters * Plays an important role in service discovery **CRD (Custom Resource Definition)** - Kubernetes * Method to define custom resources by extending the Kubernetes API * Cilium uses CRDs to define network policies, etc. **Cilium** - Cilium * Open source networking, security, and observability solution based on eBPF * Used as a Kubernetes CNI implementation ## D **DNAT (Destination Network Address Translation)** - Networking * NAT type that modifies the destination IP address of packets * Used for load balancing and port forwarding **DNS (Domain Name System)** - Networking * System that converts domain names to IP addresses * Cilium supports DNS-based network policies ## E **eBPF (extended Berkeley Packet Filter)** - eBPF * Technology that allows safe execution of programs within the Linux kernel * Core technology used in Cilium **Endpoint** - Cilium * Workload unit to which network policies are applied in Cilium * Generally corresponds to Kubernetes pods **Envoy** - Cilium * L7 proxy and service mesh component * Used for L7 policy enforcement in Cilium ## H **Hubble** - Cilium * Cilium's observability layer * Tool for real-time monitoring and analysis of network flows ## I **IPAM (IP Address Management)** - Networking * System responsible for allocating, tracking, and managing IP addresses * Cilium supports multiple IPAM modes **IPsec** - Networking * Protocol suite that provides secure communication by encrypting IP packets * Can be used for inter-node traffic encryption in Cilium ## K **kube-proxy** - Kubernetes * Network proxy that implements Kubernetes service abstraction * Cilium can replace kube-proxy ## V **VXLAN (Virtual Extensible LAN)** - Networking * Network virtualization technology that overlays Layer 2 networks over Layer 3 networks * One of Cilium's overlay networking modes ## W **WireGuard** - Networking * Modern and fast VPN protocol * Can be used for inter-node traffic encryption in Cilium ## X **XDP (eXpress Data Path)** - eBPF * eBPF feature that processes packets at the network driver level * Provides very high-performance packet processing **DaemonSet** * Kubernetes resource that runs a copy of a pod on all nodes ## E **eBPF (extended Berkeley Packet Filter)** * Technology that allows safe execution of programs within the Linux kernel **Endpoint** * Network endpoint (generally a pod) to which network policies are applied in Cilium **Envoy** * Open source edge and service proxy used as L7 proxy and communication bus ## F **FQDN (Fully Qualified Domain Name)** * Complete domain name of a host (e.g., [www.example.com](http://www.example.com)) ## G **GENEVE (Generic Network Virtualization Encapsulation)** * Encapsulation protocol for network virtualization **gRPC (gRPC Remote Procedure Call)** * High-performance RPC (Remote Procedure Call) framework developed by Google ## H **Hubble** * Cilium's network visibility and monitoring component ## I **IPAM (IP Address Management)** * Planning, tracking, and management of IP addresses **IPsec (Internet Protocol Security)** * Protocol suite for IP communication security **Istio** * Open source platform that implements service mesh ## K **Kafka** * Distributed streaming platform **kube-proxy** * Network proxy that implements Kubernetes service abstraction **Kubernetes** * Open source platform that automates deployment, scaling, and management of containerized applications ## L **L2 (Layer 2)** * Data link layer of OSI model **L3 (Layer 3)** * Network layer of OSI model **L4 (Layer 4)** * Transport layer of OSI model **L7 (Layer 7)** * Application layer of OSI model **LoadBalancer** * Device or service that distributes traffic across multiple servers ## M **MAC (Media Access Control) Address** * Unique identifier assigned to network interfaces **MTU (Maximum Transmission Unit)** * Maximum packet size that can be transmitted over a network **mTLS (mutual TLS)** * Extension of TLS where both client and server authenticate each other with certificates ## N **NAT (Network Address Translation)** * Process of modifying IP address information in IP packets **NodePort** * Kubernetes service type that exposes a static port on each node's IP ## O **OSI (Open Systems Interconnection) Model** * Conceptual model that classifies network communication into 7 abstract layers **Overlay Network** * Virtual network built on top of an existing network ## P **Pod** * Smallest deployable computing unit in Kubernetes **Proxy** * Server that acts as intermediary between client and server ## R **RBAC (Role-Based Access Control)** * Method for controlling access to system resources based on roles ## S **Service** * Abstraction in Kubernetes that provides a stable endpoint for a set of pods **SNAT (Source Network Address Translation)** * NAT type that modifies the source IP address of packets **Socket** * Endpoint for inter-process communication over a network ## T **TCP (Transmission Control Protocol)** * Connection-oriented transport protocol that provides reliable byte streams **TLS (Transport Layer Security)** * Cryptographic protocol that protects communication over networks ## U **UDP (User Datagram Protocol)** * Connectionless transport protocol ## V **VETH (Virtual Ethernet)** * Virtual ethernet device, typically created in pairs **VNI (VXLAN Network Identifier)** * 24-bit identifier that identifies VXLAN networks **VTEP (VXLAN Tunnel Endpoint)** * Endpoint responsible for encapsulation and decapsulation of VXLAN packets **VXLAN (Virtual Extensible LAN)** * Network virtualization technology that overlays Layer 2 networks over Layer 3 networks ## W **WireGuard** * Modern, fast, and secure VPN tunnel protocol ## X **XDP (eXpress Data Path)** * eBPF-based technology for very fast network packet processing ## Quiz To test what you learned in this chapter, try the [Topic Quiz](/kubernetes/en/quiz-collection/networking/cilium/glossary-quiz.md).