MetalLB Layer2 Load Balancer

This guide explains how to set up MetalLB as a Layer2 TCP/UDP load balancer for an RKE2 cluster.

For details on configuring ingress within RKE2, refer to the Ingress NGINX Controller on RKE2 Guide.

Overview

What is MetalLB?

MetalLB is a load balancer implementation for bare-metal Kubernetes clusters. In Layer2 mode, MetalLB assigns a virtual IP (VIP) to a service by broadcasting ARP requests to the local network.

Key Features

Layer2 ARP-Based VIP Management: Ideal for bare-metal and on-prem environments.
Supports TCP/UDP Traffic: Load balances both TCP and UDP traffic.
High Availability: Ensures failover between nodes for VIPs.

For more details, visit the MetalLB Documentation.

Setup Instructions

Step 1: Install MetalLB

Deploy the MetalLB Manifest:

kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.13.7/manifests/metallb.yaml

Verify the Installation: Ensure that the metallb pods are running in the metallb-system namespace:
```
kubectl get pods -n metallb-system
```

Step 2: Configure the MetalLB ConfigMap

Example: Static IP Pool Configuration

Create the ConfigMap: Define a pool of IP addresses for MetalLB to use:

apiVersion: v1
kind: ConfigMap
metadata:
  namespace: metallb-system
  name: config
data:
  config: |
    address-pools:
    - name: default
      protocol: layer2
      addresses:
      - 192.168.1.240-192.168.1.250

Apply the ConfigMap:
```
kubectl apply -f metallb-config.yaml
```

Example: DHCP Configuration

For environments where DHCP is preferred, MetalLB can integrate with external DHCP servers. Update the configuration as follows:

apiVersion: v1
kind: ConfigMap
metadata:
  namespace: metallb-system
  name: config
data:
  config: |
    address-pools:
    - name: dhcp
      protocol: layer2
      auto-assign: true

Step 3: Test MetalLB

Create a Service with LoadBalancer Type:

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
  namespace: default
spec:
  selector:
    app: nginx
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: LoadBalancer

Validate the Assigned IP:

kubectl get svc nginx-service

Expected output:

NAME            TYPE           CLUSTER-IP       EXTERNAL-IP    PORT(S)        AGE
nginx-service   LoadBalancer   10.96.0.1        192.168.1.240  80:30001/TCP   2m

Deploying MetalLB via ArgoCD

For environments leveraging ArgoCD for GitOps, you can deploy MetalLB with the following manifest:

ArgoCD Application Manifest

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: metallb
  namespace: argocd
spec:
  destination:
    namespace: metallb-system
    server: https://kubernetes.default.svc
  project: load-balancers
  source:
    repoURL: https://github.com/metallb/metallb
    targetRevision: v0.13.7
    path: manifests
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
    syncOptions:
      - CreateNamespace=true

Customizing Load Balancers

MetalLB supports custom TCP/UDP load balancer configurations. For example, to create a dedicated load balancer for ingress traffic:

Example ConfigMap Entry for Ingress Traffic

apiVersion: v1
kind: ConfigMap
metadata:
  namespace: metallb-system
  name: config
data:
  config: |
    address-pools:
    - name: ingress
      protocol: layer2
      addresses:
      - 192.168.1.200-192.168.1.210

Then, create a service with type: LoadBalancer that uses this pool:

apiVersion: v1
kind: Service
metadata:
  name: ingress-nginx
  namespace: ingress-nginx
spec:
  selector:
    app.kubernetes.io/name: ingress-nginx
  type: LoadBalancer
  ports:
    - port: 80
      targetPort: 80
    - port: 443
      targetPort: 443

Integration with RKE2

MetalLB integrates seamlessly with RKE2 clusters to provide load balancing for Kubernetes services, including the control plane and ingress traffic. For more details, refer to the Ingress NGINX Controller on RKE2 Guide.

Support Tools

MetalLB as TCP/UDP Load Balancer for RKE2