CNI Comparison 2026 Kubernetes

💡 Quick Answer: Use Cilium for eBPF-native networking with L7 policy and observability. Use Calico for mature BGP networking and wide platform support. Use Flannel for simplicity when you don’t need NetworkPolicy. Use Multus alongside any primary CNI for multi-network pods (SR-IOV, RDMA).

The Problem

Choosing a CNI plugin is one of the most impactful cluster decisions — it affects networking performance, security policy enforcement, observability, and multi-cluster connectivity. The wrong choice is hard to change later.

The Solution

CNI Feature Comparison

Feature	Cilium	Calico	Flannel	OVN-K8s
Technology	eBPF	iptables/eBPF	VXLAN	OVS/OVN
NetworkPolicy	L3/L4/L7	L3/L4	None	L3/L4
Encryption	WireGuard/IPsec	WireGuard/IPsec	None	IPsec
Observability	Hubble (built-in)	Basic	None	Basic
Service mesh	Sidecarless (eBPF)	Envoy sidecar	None	None
BGP	Yes	Yes (native)	No	No
Multi-cluster	ClusterMesh	Federation	No	IC
Windows	Partial	Yes	Yes	Yes
Bandwidth	eBPF	tc/eBPF	tc	OVS QoS
Maturity	5+ years	8+ years	8+ years	5+ years
Platform	Any K8s	Any K8s	Any K8s	OpenShift

Performance Benchmarks (Typical)

Metric	Cilium (eBPF)	Calico (eBPF)	Calico (iptables)	Flannel
Pod-to-pod latency	~0.05ms	~0.06ms	~0.1ms	~0.08ms
Throughput (10GbE)	9.8 Gbps	9.5 Gbps	8.5 Gbps	8.0 Gbps
Connection rate	180K/s	160K/s	80K/s	90K/s
CPU overhead	Low	Low	High (>1000 rules)	Low

Decision Flowchart

graph TD
    START[Choose CNI] --> NP{Need NetworkPolicy?}
    NP -->|No| FLANNEL[✅ Flannel<br/>Simple, lightweight]
    NP -->|Yes| L7{Need L7 policy?}
    L7 -->|Yes| CILIUM[✅ Cilium<br/>eBPF, Hubble, L7]
    L7 -->|No| BGP{Need BGP?}
    BGP -->|Yes| CALICO[✅ Calico<br/>Mature, BGP native]
    BGP -->|No| OCP{OpenShift?}
    OCP -->|Yes| OVN[✅ OVN-Kubernetes<br/>Default for OpenShift]
    OCP -->|No| CILIUM
    
    MULTI{Multi-NIC<br/>SR-IOV/RDMA?} --> MULTUS[Add Multus<br/>alongside primary CNI]

Install Examples

# Cilium
helm install cilium cilium/cilium --namespace kube-system \
  --set hubble.enabled=true --set hubble.relay.enabled=true

# Calico
kubectl apply -f https://raw.githubusercontent.com/projectcalico/calico/v3.28.0/manifests/calico.yaml

# Flannel
kubectl apply -f https://github.com/flannel-io/flannel/releases/latest/download/kube-flannel.yml

Common Issues

Can I change CNI after cluster creation?: Technically yes, practically painful. It requires draining all nodes, removing the old CNI, and installing the new one. Plan ahead.

Calico or Cilium for large clusters?: Both handle 5000+ nodes. Cilium’s eBPF dataplane scales better with many NetworkPolicies. Calico’s BGP is better for on-premises with existing routing infrastructure.

Best Practices

Cilium for greenfield clusters — most features, best observability
Calico for existing BGP infrastructure — native BGP support
Flannel for learning/homelab — simplest setup, no NetworkPolicy
OVN-Kubernetes for OpenShift — default and best integrated
Multus is an add-on, not a replacement — runs alongside your primary CNI

Key Takeaways

CNI choice is one of the hardest-to-change cluster decisions — choose carefully
Cilium leads in features: eBPF dataplane, L7 policy, Hubble observability, sidecarless mesh
Calico is the most mature with native BGP — best for on-premises networking
Flannel is simplest but has no NetworkPolicy support
Multus enables multi-NIC pods (SR-IOV, RDMA) alongside any primary CNI