Create subnets

Before creating an L2 template, ensure that you have the required subnets that can be used in the L2 template to allocate IP addresses for the MOSK cluster nodes. Where required, create a number of subnets for a particular project using the Subnet CR. A subnet has three logical scopes:

  • global - CR uses the default namespace. A subnet can be used for any cluster located in any project.

  • namespaced - CR uses the namespace that corresponds to a particular project where MOSK clusters are located. A subnet can be used for any cluster located in the same project.

  • cluster - CR uses the namespace where the referenced cluster is located. A subnet is only accessible to the cluster that L2Template.spec.clusterRef refers to. The Subnet objects with the cluster scope will be created for every new cluster.

You can have subnets with the same name in different projects. In this case, the subnet that has the same project as the cluster will be used. One L2 template may often reference several subnets, those subnets may have different scopes in this case.

The IP address objects (IPaddr CR) that are allocated from subnets always have the same project as their corresponding IpamHost objects, regardless of the subnet scope.

To create subnets for a cluster:

  1. Log in to a local machine where your management cluster kubeconfig is located and where kubectl is installed.

    Note

    The management cluster kubeconfig is created during the last stage of the management cluster bootstrap.

  2. Create the subnet.yaml file with a number of global or namespaced subnets depending on the configuration of your cluster:

    kubectl --kubeconfig <pathToManagementClusterKubeconfig> apply -f <SubnetFileName.yaml>
    

    Note

    In the command above and in the steps below, substitute the parameters enclosed in angle brackets with the corresponding values.

    Example of a subnet.yaml file:

    apiVersion: ipam.mirantis.com/v1alpha1
    kind: Subnet
    metadata:
      name: demo
      namespace: demo-namespace
    spec:
      cidr: 10.11.0.0/24
      gateway: 10.11.0.9
      includeRanges:
      - 10.11.0.5-10.11.0.70
      nameservers:
      - 172.18.176.6
    
    Specification fields of the Subnet object

    Parameter

    Description

    cidr (singular)

    A valid IPv4 CIDR, for example, 10.11.0.0/24.

    includeRanges (list)

    A list of IP address ranges within the given CIDR that should be used in the allocation of IPs for nodes (excluding the gateway address). The IPs outside the given ranges will not be used in the allocation. Each element of the list can be either an interval 10.11.0.5-10.11.0.70 or a single address 10.11.0.77. In the example above, the addresses 10.11.0.5-10.11.0.70 (excluding the gateway address 10.11.0.9) will be allocated for nodes. The includeRanges parameter is mutually exclusive with excludeRanges.

    excludeRanges (list)

    A list of IP address ranges within the given CIDR that should not be used in the allocation of IPs for nodes. The IPs within the given CIDR but outside the given ranges will be used in the allocation (excluding gateway address). Each element of the list can be either an interval 10.11.0.5-10.11.0.70 or a single address 10.11.0.77. The excludeRanges parameter is mutually exclusive with includeRanges.

    useWholeCidr (boolean)

    If set to true, the subnet address (10.11.0.0 in the example above) and the broadcast address (10.11.0.255 in the example above) are included into the address allocation for nodes. Otherwise, (false by default), the subnet address and broadcast address will be excluded from the address allocation.

    gateway (singular)

    A valid gateway address, for example, 10.11.0.9.

    nameservers (list)

    A list of the IP addresses of name servers. Each element of the list is a single address, for example, 172.18.176.6.

    Caution

    The subnet for the PXE network is automatically created during deployment and must contain the ipam/DefaultSubnet: "1" label. Each bare metal region must have only one subnet with this label.

    Caution

    You may use different subnets to allocate IP addresses to diffrenet components of MCC in your cluster. See below for detailed list of available options. Each subnet that is used to configure an MCC service must be labelled with special service label that starts with ipam/SVC- prefix. Make sure that no subnet has more than one such label.

  3. Optional. Add subnet for MetalLB service in your cluster. To designate a Subnet as MetalLB address pool, use label key ipam/SVC-MetalLB. Set value of the label to “1”. Set the cluster.sigs.k8s.io/cluster-name label to the name of the cluster where subnet is used. You may create multiple subnets with ipam/SVC-MetalLB label to define multiple IP address ranges for MetalLB in the cluster.

    Caution

    The IP addresses of the MetalLB address pool are not assigned to the interfaces on hosts. This is purely virtual subnet. Make sure that it is not included in the L2 template definitions for your cluster.

    Caution

    Intersection of IP address ranges within any single MetalLB address pool is not permitted. Make sure that this requirement is satisfied when configuring MetalLB address pools.

    Since MOSK 22.3, intersection of IP address ranges is verified by the bare metal provider. If intersection is identified, the MetalLB configuration will be blocked and the provider logs will contain corresponding error messages.

    Note

    • When MetalLB address ranges are defined in both cluster specification and specific 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 that are defined in both cluster specification and Subnet objects are aggregated into a single L2 address pool and sorted as strings.

  4. Optional. Technology Preview. Add a subnet for the externally accessible API endpoint of the MOSK cluster.

    • Make sure that loadBalancerHost is set to "" (empty string) in the Cluster spec.

      spec:
        providerSpec:
          value:
            apiVersion: baremetal.k8s.io/v1alpha1
            kind: BaremetalClusterProviderSpec
            ...
            loadBalancerHost: ""
      
    • Create a subnet with the ipam/SVC-LBhost label having the "1" value to make the baremetal-provider use this subnet for allocation of addresses for cluster API endpoints.

    One IP address will be allocated for each cluster to serve its Kubernetes/MKE API endpoint.

    Caution

    Make sure that master nodes have host local-link addresses in the same subnet as the cluster API endpoint address. These host IP addresses will be used for VRRP traffic. The cluster API endpoint address will be assigned to the same interface on one of the master nodes where these host IPs are assigned.

    Note

    We highly recommend that you assign the cluster API endpoint address from the LCM network. For details on cluster networks types, refer to MOSK cluster networking. See also the Single MOSK cluster use case example in the following table.

    You can use several options of addresses allocation scope of API endpoints using subnets:

    Use case

    Example configuration

    Several MOSK clusters in a region

    Create a subnet in the default namespace with no reference to any cluster.

    apiVersion: ipam.mirantis.com/v1alpha1
    kind: Subnet
    metadata:
      name: lbhost-per-region
      namespace: default
      labels:
        kaas.mirantis.com/provider: baremetal
        kaas.mirantis.com/region: region-one
        ipam/SVC-LBhost: "1"
    spec:
      cidr: 191.11.0.0/24
      includeRanges:
      - 191.11.0.6-191.11.0.20
    

    Several MOSK clusters in a project

    Create a subnet in a namespace corresponding to your project with no reference to any cluster. Such subnet has priority over the one described above.

    apiVersion: ipam.mirantis.com/v1alpha1
    kind: Subnet
    metadata:
      name: lbhost-per-namespace
      namespace: my-project
      labels:
        kaas.mirantis.com/provider: baremetal
        kaas.mirantis.com/region: region-one
        ipam/SVC-LBhost: "1"
    spec:
      cidr: 191.11.0.0/24
      includeRanges:
      - 191.11.0.6-191.11.0.20
    

    Single MOSK cluster

    Create a subnet in a namespace corresponding to your project with a reference to the target cluster using the cluster.sigs.k8s.io/cluster-name label. Such subnet has priority over the ones described above. In this case, it is not obligatory to use a dedicated subnet for addresses allocation of API endpoints. You can add the ipam/SVC-LBhost label to the LCM subnet, and one of the addresses from this subnet will be allocated for an API endpoint:

    apiVersion: ipam.mirantis.com/v1alpha1
    kind: Subnet
    metadata:
      name: lbhost-per-namespace
      namespace: my-project
      labels:
        kaas.mirantis.com/provider: baremetal
        kaas.mirantis.com/region: region-one
        ipam/SVC-LBhost: "1"
        ipam/SVC-k8s-lcm: "1"
        cluster.sigs.k8s.io/cluster-name: my-cluster
    spec:
      cidr: 10.11.0.0/24
      includeRanges:
      - 10.11.0.6-10.11.0.50
    

    The above options can be used in conjunction. For example, you can define a subnet for a region, a number of subnets within this region defined for particular namespaces, and a number of subnets within the same region and namespaces defined for particular clusters.

  5. Optional. Add a subnet(s) for the storage access network.

    • Set the ipam/SVC-ceph-public label with the value "1" to create a subnet that will be used to configure the Ceph public network.

    • Ceph will automatically use this subnet for its external connections.

    • A Ceph OSD will look for and bind to an address from this subnet when it is started on a machine.

    • Use this subnet in the L2 template for storage nodes.

    • Assign this subnet to the interface connected to your storage access network.

    When using this label, set the cluster.sigs.k8s.io/cluster-name label to the name of the target cluster during the subnet creation.

  6. Optional. Add a subnet(s) for the storage replication network.

    • Set the ipam/SVC-ceph-cluster label with the value "1" to create a subnet that will be used to configure Ceph ‘replication’ network.

    • Ceph will automatically use this subnet for its internal replication traffic.

    • Use this subnet in the L2 template for storage nodes.

    When using this label, set the cluster.sigs.k8s.io/cluster-name label to the name of the target cluster during the subnet creation.

  7. Optional. Add a subnet for Kubernetes pods traffic.

    Caution

    Use of a dedicated network for Kubernetes pods traffic, for external connection to the Kubernetes services exposed by the cluster, and for the Ceph cluster access and replication traffic is available as Technology Preview. Use such configurations for testing and evaluation purposes only. For the Technology Preview feature definition, refer to Technology Preview features.

    The following feature is still under development and will be announced in one of the following Container Cloud releases:

    • Switching Kubernetes API to listen to the specified IP address on the node

  8. Verify that the subnet is successfully created:

    kubectl get subnet kaas-mgmt -oyaml
    

    In the system output, verify the status fields of the subnet.yaml file using the table below.

    Status fields of the Subnet object

    Parameter

    Description

    statusMessage

    Contains a short state description and a more detailed one if applicable. The short status values are as follows:

    • OK - operational.

    • ERR - non-operational. This status has a detailed description, for example, ERR: Wrong includeRange for CIDR….

    cidr

    Reflects the actual CIDR, has the same meaning as spec.cidr.

    gateway

    Reflects the actual gateway, has the same meaning as spec.gateway.

    nameservers

    Reflects the actual name servers, has same meaning as spec.nameservers.

    ranges

    Specifies the address ranges that are calculated using the fields from spec: cidr, includeRanges, excludeRanges, gateway, useWholeCidr. These ranges are directly used for nodes IP allocation.

    lastUpdate

    Includes the date and time of the latest update of the Subnet RC.

    allocatable

    Includes the number of currently available IP addresses that can be allocated for nodes from the subnet.

    allocatedIPs

    Specifies the list of IPv4 addresses with the corresponding IPaddr object IDs that were already allocated from the subnet.

    capacity

    Contains the total number of IP addresses being held by ranges that equals to a sum of the allocatable and allocatedIPs parameters values.

    versionIpam

    Contains thevVersion of the kaas-ipam component that made the latest changes to the Subnet RC.

    Example of a successfully created subnet:

    apiVersion: ipam.mirantis.com/v1alpha1
    kind: Subnet
    metadata:
      labels:
        ipam/UID: 6039758f-23ee-40ba-8c0f-61c01b0ac863
        kaas.mirantis.com/provider: baremetal
        kaas.mirantis.com/region: region-one
      name: kaas-mgmt
      namespace: default
    spec:
      cidr: 10.0.0.0/24
      excludeRanges:
      - 10.0.0.100
      - 10.0.0.101-10.0.0.120
      gateway: 10.0.0.1
      includeRanges:
      - 10.0.0.50-10.0.0.90
      nameservers:
      - 172.18.176.6
    status:
      allocatable: 38
      allocatedIPs:
      - 10.0.0.50:0b50774f-ffed-11ea-84c7-0242c0a85b02
      - 10.0.0.51:1422e651-ffed-11ea-84c7-0242c0a85b02
      - 10.0.0.52:1d19912c-ffed-11ea-84c7-0242c0a85b02
      capacity: 41
      cidr: 10.0.0.0/24
      gateway: 10.0.0.1
      lastUpdate: "2020-09-26T11:40:44Z"
      nameservers:
      - 172.18.176.6
      ranges:
      - 10.0.0.50-10.0.0.90
      statusMessage: OK
      versionIpam: v3.0.999-20200807-130909-44151f8
    

Now, proceed with creating subnets for your MOSK cluster as described in Create subnets for a MOSK cluster.