CKA Services and Networking Practice Question
Which of the following CNI plugins typically uses BGP to distribute routing information across nodes?
⚠ Common exam trap
The trap here is that candidates often associate BGP only with external routing or load balancers (like MetalLB), forgetting that Calico uses BGP internally for pod-to-pod routing across nodes.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Calico
Calico uses BGP (Border Gateway Protocol) to exchange routing information between nodes, enabling direct pod-to-pod communication without overlays. Each node runs a BGP client that advertises the pod CIDRs assigned to that node, allowing the underlying network infrastructure to route traffic at Layer 3.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Calico
Why this is correct
Calico is highly regarded for its native use of the Border Gateway Protocol (BGP) to distribute routing information among Kubernetes nodes. By acting as a BGP peer, each node advertises its pod IP blocks directly to the physical network infrastructure or to a central BGP Route Reflector. This eliminates the need for packet encapsulation overhead, allowing for highly performant, bare-metal-like networking.
- ✗
Flannel
Why it's wrong here
Flannel is a simple, lightweight CNI plugin designed for easy configuration, primarily utilizing overlay network technologies like VXLAN or UDP encapsulation to route traffic. It relies on a distributed key-value store like etcd to manage IP allocations and does not natively support or implement BGP for routing distribution. This makes it less suitable for complex, non-overlay enterprise network integrations.
- ✗
Weave
Why it's wrong here
Weave Net establishes a resilient, decentralized overlay network using a proprietary gossip protocol to discover nodes and manage topology. It encapsulates pod traffic in VXLAN packets and routes them dynamically without relying on standard routing protocols like BGP. This self-configuring mesh architecture simplifies deployment but lacks the native BGP peering capabilities required for direct integration with physical routers.
- ✗
Cilium
Why it's wrong here
Cilium is fundamentally built around eBPF (Extended Berkeley Packet Filter) technology to provide high-performance data plane routing, security filtering, and load balancing. While modern versions of Cilium can integrate with BGP via MetalLB or its own built-in BGP control plane, its primary architecture is centered on eBPF-based kernel-level packet manipulation rather than traditional BGP-driven IP routing.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKA practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CKA exam.