Cilium IPAM

Use a CiliumPodIPPool as the IPAM source for an ImpNetwork instead of the internal allocator.

Prerequisites

• Cilium installed on the cluster
• CiliumPodIPPool CRD present

Auto-managed pool (recommended)

When spec.ipam.provider: cilium is set, Imp automatically creates and owns the CiliumPodIPPool. You only need to reference it by name:

apiVersion: imp.dev/v1alpha1
kind: ImpNetwork
metadata:
  name: vm-net-a
  namespace: default
spec:
  subnet: 10.44.0.0/24
  ipam:
    provider: cilium
    cilium:
      poolRef: vm-net-a   # Imp creates this pool automatically

The pool CIDR defaults to spec.subnet. Override with spec.ipam.cilium.cidr:

spec:
  ipam:
    cilium:
      poolRef: vm-net-a
      cidr: 10.77.0.0/24   # use a different CIDR for the pool

The pool is deleted when the ImpNetwork is deleted.

Manual pool (advanced)

To manage the CiliumPodIPPool yourself, create it before the ImpNetwork and set the same poolRef. Imp will not modify a pool it does not own.

Example manual pool:

apiVersion: cilium.io/v2alpha1
kind: CiliumPodIPPool
metadata:
  name: vm-net-a
spec:
  ipv4:
    cidrs:
      - 10.77.0.0/24
    maskSize: 30

spec.subnet is still required for API compatibility. VM IP allocation uses the Cilium pool CIDR.

Verify

kubectl get ciliumpodippool vm-net-a -o yaml
kubectl get impnetwork vm-net-a -n default -o jsonpath='{.spec.ipam.cilium.poolRef}'
kubectl -n imp-system logs ds/imp-agent | grep -i ipam

Failure Modes

Symptom	Cause	Fix
VM start fails, agent logs show pool lookup failure	CiliumPodIPPool missing	Create pool or correct poolRef
Allocation subnet resolution error	Pool has no spec.cidrs	Configure CIDR in pool
Pool lookup fails entirely	Cilium CRD not installed	Install Cilium or set provider: internal

Rollback

kubectl patch impnetwork vm-net-a -n default \
  --type=merge -p '{"spec":{"ipam":{"provider":"internal"}}}'