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MetalLB

Purpose: Load balancer for bare-metal Kubernetes clusters

Version: 0.14.8

Namespace: metallb-system

Description​

Provides network load balancing for clusters that don't run on a cloud provider with built-in load balancers. Uses Layer 2 (ARP) mode for IP address announcement.

Installation​

Installed via ArgoCD from Helm chart: metallb/metallb

Configuration​

Configuration is managed via cluster-configs.yaml template which creates:

IPAddressPool​

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: default-pool
  namespace: metallb-system
spec:
  addresses:
    - 10.0.0.210-10.0.0.250
  autoAssign: true

Pool Range: 10.0.0.210 - 10.0.0.250 (41 addresses)

L2Advertisement​

apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
  name: default
  namespace: metallb-system
spec:
  ipAddressPools:
    - default-pool

Usage​

Services of type LoadBalancer automatically get an IP from the pool:

kubectl get svc -n ingress-nginx
# NAME                       TYPE           CLUSTER-IP     EXTERNAL-IP   PORT(S)
# ingress-nginx-controller   LoadBalancer   10.96.89.123   10.0.0.211   80:30081/TCP,443:30080/TCP

Example Service​

apiVersion: v1
kind: Service
metadata:
  name: my-app
  namespace: default
spec:
  type: LoadBalancer
  ports:
    - port: 80
      targetPort: 8080
  selector:
    app: my-app

Components​

ComponentPurpose
metallb-controllerIP address allocation and management
metallb-speakerARP announcer (runs as DaemonSet)

How It Works​

  1. User creates a Service with type: LoadBalancer
  2. MetalLB controller assigns an IP from the pool
  3. MetalLB speaker announces the IP via ARP on the local network
  4. External traffic to the IP is routed to the service

Troubleshooting​

Check IP Pool Status​

kubectl get ipaddresspool -n metallb-system
kubectl get l2advertisement -n metallb-system

Check Speaker Pods​

kubectl get pods -n metallb-system -l component=speaker
kubectl logs -n metallb-system -l component=speaker

Common Issues​

  1. No IPs available - Pool exhausted; expand the address range
  2. ARP not working - Check network allows ARP broadcasts
  3. Firewall blocking - Ensure firewalld/iptables allows traffic