Discuss Linux Foundation Cilium-Associate Exam Topic 7 Question 3

What is correct about the Kubernetes Host Scope IP Address Management (IPAM) mode?

AIt supports multiple CIDRs (Classless Inter-Domain Routing) per cluster

BIt supports multiple CIDRs (Classless Inter-Domain Routing) per node.

CIt can beset by using the ipam: crd configuration flag.

DIt supports both tunnel and direct routing modes.

Suggested Answer: D

Kubernetes host-scope IPAM can be used with both Cilium tunnel routing and native direct routing. The IPAM mechanism determines how each node receives and locally allocates pod addresses; it does not inherently require a particular packet-forwarding model. The current IPAM feature matrix explicitly marks both tunnel routing and direct routing as supported for Kubernetes host-scope mode.

In this mode, Kubernetes allocates a PodCIDR to each node and publishes it through the standard v1.Node resource, normally in spec.podCIDR or spec.podCIDRs. The Cilium agent waits for the relevant range and allocates individual pod addresses from that node-specific CIDR. The correct configuration is ipam: kubernetes or the Helm equivalent ipam.mode=kubernetes, not ipam: crd; therefore, C is false.

The documented feature matrix does not provide multiple CIDRs per cluster or multiple CIDRs per node for this mode, eliminating A and B. Multi-pool IPAM is the Cilium mode designed for allocating per-node CIDRs from multiple configurable pools.

Because Kubernetes host-scope IPAM supports either overlay tunneling or direct routing while the other statements contradict its capabilities or configuration, D is correct.

Official references

IP Address Management; Kubernetes Host Scope.

Study Guide topic: Installation and Configuration.

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8 comments · newest first

Malcolm 3 days ago

B is misleading, it doesn't support multiple CIDRs per node.

Laurene 8 days ago

Wait, can it really do both tunnel and direct routing?

Kanisha 13 days ago

Totally agree, that's a key feature!

Marsha 19 days ago

A is correct, it does support multiple CIDRs per cluster.

Paris 24 days ago

I remember discussing routing modes in class, and I think option D is definitely relevant to how Kubernetes handles networking.

Cristy 29 days ago

I vaguely recall something about the ipam: crd flag, so option C could be a possibility, but I need to double-check that.

Moira 1 month ago

I'm not entirely sure, but I feel like option B might be correct since nodes often have their own IP ranges.

Thad 1 month ago

I think option A sounds familiar because I remember reading about CIDRs in relation to cluster networking.

Linux Foundation Cilium-Associate Exam - Topic 7 Question 3 Discussion