Cloud & Containers Cilium-Associate Linux Foundation Study Notes

Technical explanation

Cilium derives a workload’s security identity from its security-relevant labels. Network policies then refer to workload characteristics such as application, role, environment, namespace, or service account rather than depending exclusively on transient pod IP addresses. The identity is associated with traffic in the Cilium datapath and validated when policy is enforced. This makes B the accurate description.

The identity is not limited to a single pod. Endpoints that have the same set of identity-relevant labels can share the same numeric security identity, including endpoints located on different cluster nodes. This reduces policy-map growth and allows policy to scale with logical application groups rather than with the number of pod addresses. Namespace information is normally among the labels used to derive identity, but that does not make an identity inherently “tied to a single namespace” as option A states.

Options C and D invert Cilium’s design. IP addresses remain necessary for packet delivery, but they are not the primary security identifier for Cilium-managed workloads. Pods can be recreated and assigned new addresses while retaining the same relevant labels and therefore the same security intent. Decoupling identity from addressing is precisely what improves scalability and operational stability.

Official references

Cilium Terminology and Identity ; Introduction to Cilium and Hubble .

Study Guide topic: Architecture.

Technical explanation

Kubernetes kube-proxy conventionally implements Service translation and load balancing through either iptables or IPVS. With Cilium’s kube-proxy replacement enabled, eBPF programs and maps perform Kubernetes Service handling directly in the kernel, including ClusterIP, NodePort, LoadBalancer, ExternalIP, and related service translation functions. C is therefore correct.

The replacement can operate at socket hooks and packet-processing hooks. Service and backend information is stored in eBPF maps, allowing the datapath to select backends and perform address translation without traversing the kube-proxy-generated iptables or IPVS rules normally used for Kubernetes Services.

BGP is not replaced. Cilium’s BGP Control Plane is a separate feature used to advertise routes and service addresses to external routers. Routing itself is also not eliminated; Cilium can implement and accelerate routing decisions with eBPF, but packets still require a valid forwarding model. firewalld is a host firewall-management service and is not the underlying Kubernetes Service implementation replaced by kube-proxy replacement.

Relevant installations must satisfy the kernel and device requirements for Cilium’s eBPF service load-balancer functionality.

Official references

Kubernetes Without kube-proxy

Study Guide topic: kube-proxy replacement, eBPF service maps, iptables, and IPVS.

Cilium's official documentation confirms that a CiliumEgressGatewayPolicy selects traffic originating from matching pods , routes traffic destined for the configured destinationCIDRs through the selected egress gateway node, and SNATs that traffic using the configured egressIP.

Technical explanation

The intended answer is A because API request limiting corresponds to rate limiting, which Cilium identifies as a core Layer 7 traffic-management capability. Cilium combines its eBPF datapath with Envoy for application-layer processing. The official Service Mesh documentation expressly includes rate limiting among the functions that must understand protocols such as HTTP, REST, gRPC, and WebSocket. It is therefore not merely packet-rate policing at Layer 3 or Layer 4; it can be applied with application-protocol context.

However, this question is no longer valid as a strict single-answer item. Current Cilium documentation also describes proxy-based Layer 7 load balancing as useful for gRPC and provides an Envoy-backed implementation for Kubernetes Services. Consequently, option C is also supportable under the current product documentation, although the feature is identified as beta. API authorization and fault-delay injection are not presented as equivalent first-class Cilium Service Mesh use cases in the cited feature overview.

For certification-bank purposes, retain A as the intended answer, but revise option C or qualify it to restore a unique correct choice.

Official references

Service Mesh ; Proxy Load Balancing for Kubernetes Services .

Study Guide topic: Service Mesh.