MetalLB load balancer

MetalLB is a load balancer designed for bare metal Kubernetes clusters that uses standard routing protocols.

Prerequisites

• An MKE cluster that does not already have load-balancing functionality.

• A MetalLB-compatible cluster network configuration.

• kube-proxy running in iptables mode.

• The absence of any cloud provider configuration.

Configuration

MetalLB is configured through the addons section of the MKE 4 configuration file. The function is disabled by default, and thus to use MetalLB you must set the enabled parameter to true.

MetalLB example configuration:

spec:
  addons:
    - chart:
        name: metallb
        repo: https://metallb.github.io/metallb
        values: |
          controller:
            tolerations:
              - key: node-role.kubernetes.io/master
                operator: Exists
                effect: NoSchedule
          speaker:
            frr:
              enabled: false          
        version: 0.14.7
      dryRun: false
      enabled: true
      kind: chart
      name: metallb
      namespace: metallb-system

To configure MetalLB:

1. Obtain the default MKE 4 configuration file:

   mkectl init

2. Set the enabled parameter for metallb in the addons section to true.

3. Apply the configuration:

   mkectl apply -f <mke-configuration-file>

4. Verify the successful deployment of MetalLB in the cluster:

   kubectl get pods,services,deployments -n metallb-system -l app.kubernetes.io/name=metallb

   Example output:

   NAME                                      READY   STATUS    RESTARTS   AGE
   pod/metallb-controller-79d6b8bb85-c2hrm   1/1     Running   0          17m
   pod/metallb-speaker-ccpdf                 1/1     Running   0          17m
   pod/metallb-speaker-x2pgf                 1/1     Running   0          17m
   
   NAME                              TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)   AGE
   service/metallb-webhook-service   ClusterIP   10.96.8.155   none          443/TCP   17m
   
   NAME                                 READY   UP-TO-DATE   AVAILABLE   AGE
   deployment.apps/metallb-controller   1/1     1            1           17m

Configuration parameters

The default configuration parameters for the MetalLB add-on are detailed in the following table:

An MKE version comparison for MetalLB configuration parameters is offered in the following table:

IP address pool configuration

Support for IP address pool configuration is deprecated in MKE 4, and as such the configuration must now be managed independently.

Create IP address pools in a fresh installation

For information on how to create IP address pools, refer to the official MetalLB documentation, Layer 2 configuration.

The following example configuration gives MetalLB control over IPs from 192.168.1.240 to 192.168.1.250, and configures Layer 2 mode.

---
apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: cheap
  namespace: metallb-system
spec:
  addresses:
  - 192.168.10.0/24
---
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
  name: empty
  namespace: metallb-system

As necessary, refer to the official MetalLB documentation, Advanced AddressPool.

Managing IP address pools during upgrade

During an upgrade from MKE 3 to MKE 4, if metalLB is enabled in the former the configured IP address pool details display in the upgrade summary.

The following example configuration presents MetalLB enabled in MKE 3:

[cluster_config.metallb_config]
  enabled = true

  [[cluster_config.metallb_config.metallb_ip_addr_pool]]
    name = "example1"
    external_ip = ["192.168.10.0/24", "192.168.1.0/24"]
  [[cluster_config.metallb_config.metallb_ip_addr_pool]]
    name = "example2"
    external_ip = ["192.155.10.0/24"]

The upgrade summary presents as follows:

MetalLB IP address pools
---------------
name: example1
ipaddress: [192.168.10.0/24 192.168.1.0/24]

name: example2
ipaddress: [192.155.10.0/24]

Please make sure that you create these pools after MKE4 installation is complete.

Refer to the upgrade summary for guidance in the creation of IP address pools. To create the pools, you can use the template that follows or consult the official MetalLB documentation Layer 2 configuration for assistance.

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: example1
  namespace: metallb-system
spec:
  addresses:
  - 192.168.10.0/24
  - 192.168.1.0/24
---
apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: example2
  namespace: metallb-system
spec:
  addresses:
  - 192.155.10.0/24
---
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
  name: empty
  namespace: metallb-system

Request specific IP address pools

With MetalLB, you can request assignment from a specific address pool, if you prefer a particular IP address type but do not require an exact address. To do this, add metallb.universe.tf/address-pool to your service, setting the annotation value to the name of your chosen address pool.

MetalLB example configuration:

apiVersion: v1
kind: Service
metadata:
  name: nginx
  annotations:
    metallb.universe.tf/address-pool: production-public-ips
spec:
  ports:
  - port: 80
    targetPort: 80
  selector:
    app: nginx
  type: LoadBalancer

For more information, refer to the official MetalLB documentation Requesting specific IPs.

Uninstall MetalLB

1. Obtain the MKE 4 configuration file.

2. Set the enabled field to false to disable MetalLB.

   mkectl <mke-configuration-file>

3. Apply the configuration:

   mkectl apply -f <mke-configuration-file>