iptables vs IPVS: What to Use for Kubernetes?

Kubernetes supports two main kube-proxy modes: iptables and ipvs. Which one should you use?

1. What is kube-proxy?

kube-proxy manages network rules on Kubernetes nodes, allowing communication between services and pods. It can operate in different modes: iptables, ipvs, and userspace (deprecated).

2. iptables Mode

• Default and widely supported
• Implements rules using iptables NAT chains
• Pros:
  • Simpler
  • No extra kernel modules required
  • Easier to debug
• Cons:
  • Performance degrades with many services
  • Sequential rule processing

3. IPVS Mode

• Based on Linux IP Virtual Server (part of LVS)
• Uses a hash table for rules → faster performance
• Pros:
  • Better performance for large-scale clusters
  • Supports connection-level load balancing algorithms (round-robin, least connections, etc.)
• Cons:
  • Requires ip_vs kernel modules
  • Slightly more complex setup

4. Switching to IPVS

Check kernel support:

lsmod | grep ip_vs

Install required modules:

modprobe ip_vs
modprobe ip_vs_rr

Enable IPVS mode in kubeadm:

apiVersion: kubeproxy.config.k8s.io/v1alpha1
kind: KubeProxyConfiguration
mode: "ipvs"

Then initialize or reconfigure kube-proxy accordingly.

5. When to Use Which?

Use IPVS if you’re running a large cluster or need advanced load balancing.
Use iptables if simplicity and compatibility are your priorities.

Conclusion

Both iptables and IPVS are valid kube-proxy backends. Choose based on your cluster scale, performance needs, and operational complexity.