Configure MetalLB

This section describes how to set up and verify MetalLB parameters during configuration of subnets for a MOSK cluster creation.

Configuration rules for ‘MetalLBConfig’ and ‘MetalLBConfigTemplate’ objects

Caution

The use of the MetalLBConfig object is mandatory after your management cluster upgrade to the Cluster release 17.0.0.

The following rules and requirements apply to configuration of the MetalLBConfig and MetalLBConfigTemplate objects:

  • Define one MetalLBConfig and MetalLBConfigTemplate object per cluster.

  • Define the following mandatory labels:

    cluster.sigs.k8s.io/cluster-name

    Specifies the cluster name where the MetalLB address pool is used.

    kaas.mirantis.com/region

    Specifies the region name of the cluster where the MetalLB address pool is used.

    kaas.mirantis.com/provider

    Specifies the provider of the cluster where the MetalLB address pool is used.

  • You can use MetalLBConfig without MetalLBConfigTemplate but not the opposite way.

  • You can use the MetalLBConfig and MetalLBConfigTemplate objects to optimize address announcement for load-balanced services using the interfaces selector for the l2Advertisements object. This selector allows for announcing addresses only on selected host interfaces. For details, see Container Cloud API Reference: MetalLBConfigTemplate spec.

    Mirantis recommends this configuration if nodes use separate host networks for different types of traffic. The advantages of such configuration include reduced congestion on other interfaces and networks, as well as limited exposure of addresses of load-balanced services to irrelevant interfaces and networks.

  • When using MetalLBConfigTemplate:

    • MetalLBConfig must reference MetalLBConfigTemplate by name:

      spec:
        templateName: <managed-metallb-template>
      
    • You can use Subnet objects for defining MetalLB address pools. Refer to MetalLB configuration guidelines for subnets for guidelines on configuring MetalLB address pools using Subnet objects.

    The use of MetalLBConfigTemplate object gives more flexibility when describing MetalLB configuration as it allows using variables, functions, and the Go template expressions inside object templates.

  • Intersection of IP address ranges within any single MetalLB address pool is not allowed.

  • At least one MetalLB address pool must have the auto-assign policy enabled so that unannotated services can have load balancer IPs allocated for them.

  • When configuring multiple address pools with the auto-assign policy enabled, keep in mind that it is not determined in advance which pool of those multiple address pools is used to allocate an IP for a particular unannotated service.

Configure and verify MetalLB

  1. Optional. Configure parameters related to MetalLB components life cycle such as deployment and update using the metallb Helm chart values in the Cluster spec section. For example:

  2. Configure the MetalLB parameters related to IP address allocation and announcement for load-balanced cluster services:

    Select from the following options:

    • Mandatory after a management cluster upgrade to the Cluster release 17.0.0. Recommended and default since MOSK 23.2 in the Technology Preview scope. Create MetalLBConfig and MetalLBConfigTemplate objects. This method allows using the Subnet object to define MetalLB address pools.

      Since MOSK 23.2.2, in the Technology Preview scope, you can use BGP for announcement of external addresses of Kubernetes load-balanced services for a MOSK cluster. To configure the BGP announcement mode for MetalLB, use MetalLBConfig and MetalLBConfigTemplate objects.

      The use of BGP is required to announce IP addresses for load-balanced services when using MetalLB on nodes that are distributed across multiple racks. In this case, setting of rack-id labels on nodes is required, they are used in node selectors for BGPPeer, BGPAdvertisement, or both MetalLB objects to properly configure BGP connections from each node.

      Configuration example of the Machine object for the BGP announcement mode
      apiVersion: cluster.k8s.io/v1alpha1
      kind: Machine
      metadata:
        name: test-cluster-compute-1
        namespace: mosk-ns
        labels:
          cluster.sigs.k8s.io/cluster-name: test-cluster
          ipam/RackRef: rack-1  # reference to the "rack-1" Rack
          kaas.mirantis.com/provider: baremetal
          kaas.mirantis.com/region: region-one
      spec:
        providerSpec:
          value:
            ...
            nodeLabels:
            - key: rack-id   # node label can be used in "nodeSelectors" inside
              value: rack-1  # "BGPPeer" and/or "BGPAdvertisement" MetalLB objects
        ...
      
      Configuration example of the MetalLBConfigTemplate object for the BGP announcement mode
      apiVersion: ipam.mirantis.com/v1alpha1
      kind: MetalLBConfigTemplate
      metadata:
        name: test-cluster-metallb-config-template
        namespace: mosk-ns
        labels:
          cluster.sigs.k8s.io/cluster-name: test-cluster
          kaas.mirantis.com/provider: baremetal
          kaas.mirantis.com/region: region-one
      spec:
        templates:
          ...
          bgpPeers: |
            - name: svc-peer-1
              spec:
                peerAddress: 10.77.42.1
                peerASN: 65100
                myASN: 65101
                nodeSelectors:
                  - matchLabels:
                      rack-id: rack-1  # references the nodes having
                                       # the "rack-id=rack-1" label
          bgpAdvertisements: |
            - name: services
              spec:
                ipAddressPools:
                  - services
                peers:
                  - svc-peer-1
                  ...
      

      The bgpPeers and bgpAdvertisements fields are used to configure BGP announcement instead of l2Advertisements.

      The use of BGP for announcement also allows for better balancing of service traffic between cluster nodes as well as gives more configuration control and flexibility for infrastructure administrators. For configuration examples, refer to Examples of MetalLBConfigTemplate. For configuration procedure, refer to Configure BGP announcement for cluster API LB address.

    • Not recommended. Configure the configInline value in the MetalLB chart of the Cluster object.

      Warning

      This option is deprecated since MOSK 23.2 and is removed during the management cluster upgrade to the Cluster release 17.0.0, which is introduced in Container Cloud 2.25.0.

      Therefore, this option becomes unavailable on MOSK 23.2 clusters after the parent management cluster upgrade to 2.25.0.

    • Not recommended. Configure the Subnet objects without MetalLBConfigTemplate.

      Warning

      This option is deprecated since MOSK 23.2 and is removed during the management cluster upgrade to the Cluster release 17.0.0, which is introduced in Container Cloud 2.25.0.

      Therefore, this option becomes unavailable on MOSK 23.2 clusters after the parent management cluster upgrade to 2.25.0.

    Caution

    If the MetalLBConfig object is not used for MetalLB configuration related to address allocation and announcement for load-balanced services, then automated migration applies during cluster creation or update to MOSK 23.2.

    During automated migration, the MetalLBConfig and MetalLBConfigTemplate objects are created and contents of the MetalLB chart configInline value is converted to the parameters of the MetalLBConfigTemplate object.

    Any change to the configInline value made on a MOSK 23.2 cluster will be reflected in the MetalLBConfigTemplate object.

    This automated migration is removed during your management cluster upgrade to the Cluster release 17.0.0, which is introduced in Container Cloud 2.25.0, together with the possibility to use the configInline value of the MetalLB chart. After that, any changes in MetalLB configuration related to address allocation and announcement for load-balanced services are applied using the MetalLBConfig, MetalLBConfigTemplate, and Subnet objects only.

    Select from the following options:

    • Configure Subnet objects. For details, see MetalLB configuration guidelines for subnets.

    • Configure the configInline value for the MetalLB chart in the Cluster object.

    • Configure both the configInline value for the MetalLB chart and Subnet objects.

      The resulting MetalLB address pools configuration will contain address ranges from both cluster specification and Subnet objects. All address ranges for L2 address pools will be aggregated into a single L2 address pool and sorted as strings.

    Changes to be applied since MOSK 23.2

    The configuration options above become deprecated since 23.2, and automated migration of MetalLB parameters applies during cluster creation or update to MOSK 23.2.

    During automated migration, the MetalLBConfig and MetalLBConfigTemplate objects are created and contents of the MetalLB chart configInline value is converted to the parameters of the MetalLBConfigTemplate object.

    Any change to the configInline value made on a MOSK 23.2 cluster will be reflected in the MetalLBConfigTemplate object.

    This automated migration is removed during your management cluster upgrade to Container Cloud 2.25.0 together with the possibility to use the configInline value of the MetalLB chart. After that, any changes in MetalLB configuration related to address allocation and announcement for load-balanced services will be applied using the MetalLBConfigTemplate and Subnet objects only.

  3. Verify the current MetalLB configuration:

    Verify the MetalLB configuration that is stored in MetalLB objects:

    kubectl -n metallb-system get ipaddresspools,l2advertisements
    

    The example system output:

    NAME                                    AGE
    ipaddresspool.metallb.io/default        129m
    ipaddresspool.metallb.io/services-pxe   129m
    
    NAME                                      AGE
    l2advertisement.metallb.io/default        129m
    l2advertisement.metallb.io/services-pxe   129m
    

    Verify one of the listed above MetalLB objects:

    kubectl -n metallb-system get <object> -o json | jq '.spec'
    

    The example system output for ipaddresspool objects:

    $ kubectl -n metallb-system get ipaddresspool.metallb.io/default -o json | jq '.spec'
    {
      "addresses": [
        "10.0.11.61-10.0.11.80"
      ],
      "autoAssign": true,
      "avoidBuggyIPs": false
    }
    $ kubectl -n metallb-system get ipaddresspool.metallb.io/services-pxe -o json | jq '.spec'
    {
      "addresses": [
        "10.0.0.61-10.0.0.70"
      ],
      "autoAssign": false,
      "avoidBuggyIPs": false
    }
    

    Verify the MetalLB configuration that is stored in the ConfigMap object:

    kubectl -n metallb-system get cm metallb -o jsonpath={.data.config}
    

    An example of a successful output:

    address-pools:
    - name: default
      protocol: layer2
      addresses:
      - 10.0.11.61-10.0.11.80
    - name: services-pxe
      protocol: layer2
      auto-assign: false
      addresses:
      - 10.0.0.61-10.0.0.70
    

    The auto-assign parameter will be set to false for all address pools except the default one. So, a particular service will get an address from such an address pool only if the Service object has a special metallb.universe.tf/address-pool annotation that points to the specific address pool name.