Pass the Linux Foundation Cloud & Containers Cilium-Associate Questions and answers with ExamsMirror

Technical explanation

D is the accurate general description because eBPF programs can attach at kernel and application-related hook points where data may already be decrypted, depending on the program and the selected hook. The statement says “could,” not that every packet-processing eBPF program automatically decrypts TLS. Cilium’s documented TLS-aware inspection uses controlled TLS termination and a userspace Envoy proxy; the broader point is that eBPF is not restricted to observing encrypted wire-format packets at a single network interface.

The other choices are directly contradicted by Cilium’s eBPF documentation. XDP and traffic-control programs can be replaced atomically at runtime without rebooting the host or restarting network services, so A is false. Traffic-control BPF supports both ingress and egress hook points, making B false. Cilium also applies eBPF-based security to the host through its Host Firewall and host-policy capabilities; therefore, eBPF security is not inherently confined to container traffic, and C is false.

A critical distinction is that inspecting application plaintext depends on where the program attaches and where encryption occurs. Cilium’s ordinary L3/L4 datapath does not magically decrypt TLS, while its documented TLS interception workflow explicitly terminates and re-originates selected connections to expose application-layer content.

Official references

Cilium eBPF program types ; eBPF datapath introduction ; Inspecting TLS Encrypted Connections .

Study Guide topic: eBPF.

Technical explanation

D most precisely describes Cilium’s foundational use of eBPF. The Cilium agent translates desired networking and security state into eBPF programs and maps, then attaches those programs to Linux kernel hook points such as traffic-control ingress and egress, XDP, cgroups, and sockets. Packets can consequently be classified, permitted, dropped, redirected, load-balanced, or forwarded without requiring changes to the protected application.

Endpoint-policy programs associate traffic with Cilium security identities and perform Layer 3 and Layer 4 enforcement in the kernel. Traffic requiring Layer 7 inspection can be redirected from the eBPF datapath to Envoy. This combination provides efficient kernel-level enforcement while retaining application-aware controls.

Option A describes an important Hubble observability outcome, but it is narrower than Cilium’s primary networking and enforcement model and overstates what is necessarily exposed through a UI. Option B mischaracterizes Cilium as DNS infrastructure; Cilium can enforce DNS-aware policies but does not replace Kubernetes DNS service discovery. Option C is too generic and implies a conventional threat-detection product rather than identity-based networking and policy enforcement.

Official references

Cilium eBPF Datapath Introduction , Introduction to Cilium and Hubble

Study Guide topic: Kernel hooks, endpoint policy, identities, and eBPF datapath enforcement.

Technical explanation

The official IPAM documentation expressly states that the safest way to change IPAM mode is to install a fresh Kubernetes cluster using the required new IPAM configuration. A live cluster already contains allocated workload addresses, node routing state, Cilium endpoint state, service state, and potentially cloud-provider resources that depend on the active allocator. Replacing the allocator in place can invalidate these assumptions and cause persistent connectivity disruption rather than merely a short agent restart.

Updating a Kubernetes Node object does not generally convert Cilium’s IPAM mode. The responsible resource and allocation behavior depend on the selected mode: Kubernetes host-scope IPAM, cluster-pool IPAM, multi-pool IPAM, CRD-backed modes, and cloud-specific allocators manage address information differently. Restarting agents after changing a configuration value likewise does not constitute a safe migration plan, because existing endpoints and routes may retain state created under the former allocator.

Cilium advises against changing the IPAM mode of an existing cluster unless a specifically documented migration procedure applies. The currently documented exception is migration from cluster-pool IPAM to multi-pool IPAM. As the question provides no such constrained scenario, D is the unambiguously safest answer.

Official references

IP Address Management .

Study Guide topic: Installation and Configuration.

Technical explanation

C is not a valid description. A service-mesh sidecar externalizes networking functions into a proxy container running beside the application; it does not force the instrumentation logic into the application’s source code. In fact, a core service-mesh objective is to provide connectivity, security, traffic management, and observability transparently without requiring application-code changes.

The operational concerns in the other choices are characteristic of sidecar implementations. A proxy must be injected into each workload pod, increasing container count and potentially affecting pod initialization, resource consumption, ordering, and readiness. Adding a sidecar to an existing pod template normally requires the pods to be recreated because Kubernetes cannot dynamically add a new container to an already-running pod.

Traffic interception also directs application traffic through the sidecar proxy and its network namespace paths, adding network-stack traversal and proxy-processing overhead. Cilium’s service-mesh design can instead use node-level Envoy proxies together with eBPF traffic redirection, avoiding one proxy container in every application pod. This preserves transparent application behavior while reducing the per-workload operational burden.

Official references

Cilium Service Mesh , Cilium Ingress and Network Policy Example

Study Guide topic: Sidecar-based and sidecar-free service-mesh architectures.

Technical explanation

A Cluster Mesh can be created after assigning each cluster a unique name and numeric cluster ID. Cilium uses the cluster ID when constructing Cluster Mesh security identities, so duplicate values cannot safely identify endpoints from different clusters. The name must likewise be unique. These values can be changed after installation, although all existing workloads must then be restarted so their security identities are regenerated.

The other listed conditions are compatible. Both clusters use the same encapsulation datapath mode, their PodCIDRs are intended to be non-overlapping, and the nodes possess the required inter-cluster connectivity. Different Kubernetes patch or minor versions do not inherently prevent Cluster Mesh. Cilium versions may differ by one minor release, so versions 1.14 and 1.13 satisfy the documented compatibility rule.

Different certificate authorities are not an irreversible blocker under current documentation. Every cluster must trust certificates presented by the others. Operators may use a shared root CA or configure a CA bundle containing all trusted CA certificates. Consequently, B is too absolute. C is also false because changing the cluster identity is possible, subject to workload restarts. D is unnecessary because a one-minor Cilium difference is supported.

The source’s option A is truncated, but its intended corrective action is technically accurate.

Official references

Setting up Cluster Mesh .

Study Guide topic: Cluster Mesh.

Technical explanation

Cilium uses Envoy as its userspace Layer 7 proxy. When a Cilium policy contains HTTP or another supported application-layer rule, Cilium’s eBPF datapath identifies matching traffic and redirects it to a node-local Envoy instance. Envoy evaluates the application-layer attributes—such as HTTP method, path, or headers—against the generated policy configuration and then forwards or rejects the request.

The proxy can operate in embedded mode as a separate process inside the Cilium agent pod or as the independently life-cycled cilium-envoy DaemonSet. Both deployment forms use Cilium’s optimized Envoy distribution and custom policy-enforcement filters. Communication between the agent and Envoy uses local UNIX-domain sockets for configuration, access logs, and administrative operations.

HAProxy is a capable general-purpose load balancer, but it is not Cilium’s L7 policy proxy. Squid primarily serves forward and caching proxy use cases. linkerd2-proxy belongs to the Linkerd service mesh and is not used by Cilium for network-policy enforcement. Consequently, only D identifies the proxy integrated into Cilium’s L7 datapath.

Official references

Cilium Envoy , Cilium eBPF Datapath Introduction

Study Guide topic: Envoy proxy integration and Layer 7 policy enforcement.

Technical explanation

Both Kubernetes Ingress and the north-south use of Gateway API provide declarative Layer 7 routing from clients outside the cluster to Kubernetes workloads. They express host- and path-based routing through Kubernetes resources and can be implemented by controllers such as Cilium’s Envoy-based ingress implementation. A therefore captures their shared purpose most accurately.

The remaining choices describe differences rather than universal similarities. Gateway API is explicitly role-oriented: infrastructure administrators manage GatewayClass and often Gateway , while application owners manage route resources such as HTTPRoute . The Ingress API does not provide the same formal separation of administrative and application-facing resources, making C unsuitable as a statement about both.

Implementation-specific annotations are historically common with Ingress because its core API is limited. Gateway API was deliberately designed with more expressive, portable resource fields so that implementations do not need to depend as heavily on vendor-specific annotations; D is consequently not true of both. Namespace behavior also differs because Gateway API provides controlled cross-namespace attachment and reference mechanisms. B is therefore not the defining common capability.

Official references

Cilium Kubernetes Ingress Support , Cilium Gateway API Support , Migrating from Ingress to Gateway API

Study Guide topic: Kubernetes north-south routing, Ingress, and Gateway API.

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.