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Configuring MetalLB address pools

To allocate and manage the IP addresses assigned to load balancer services, configure MetalLB address pool custom resources. Defining these pools ensures that application workloads remain reachable through designated network ranges for consistent external access.

The namespaces used in the examples show metallb-system as the namespace.

For more information about how to install the MetalLB Operator, see About MetalLB and the MetalLB Operator.

About the IPAddressPool custom resource

To define the IP address ranges available for load balancer services, configure the properties of the MetalLB IPAddressPool custom resource (CR).

The following table details the parameters for the IPAddressPool CR:

Table 1. MetalLB IPAddressPool pool custom resource
Parameter Type Description

metadata.name

string

Specifies the name for the address pool. When you add a service, you can specify this pool name in the metallb.io/address-pool annotation to select an IP address from a specific pool. The names doc-example, silver, and gold are used throughout the documentation.

metadata.namespace

string

Specifies the namespace for the address pool. Specify the same namespace that the MetalLB Operator uses.

metadata.label

string

Optional: Specifies the key-value pair assigned to the IPAddressPool. This can be referenced by the ipAddressPoolSelectors in the BGPAdvertisement and L2Advertisement CRD to associate the IPAddressPool with the advertisement

spec.addresses

string

Specifies a list of IP addresses for the MetalLB Operator to assign to services. You can specify multiple ranges in a single pool, where these ranges all share the same settings. Specify each range in Classless Inter-Domain Routing (CIDR) notation or as starting and ending IP addresses separated with a hyphen.

spec.autoAssign

boolean

Optional: Specifies whether the MetalLB Operator automatically assigns IP addresses from this pool. Specify false if you want to explicitly request an IP address from this pool with the metallb.io/address-pool annotation. The default value is true.

For IP address pool configurations, ensure the addresses parameter specifies only IP addresses that are available and not in use by other network devices, especially gateway addresses, to prevent conflicts when autoAssign is enabled.

spec.avoidBuggyIPs

boolean

Optional: When you set the parameter to enabled, the IP addresses ending .0 and .255 are not allocated from the pool. The default value is false. Some older consumer network equipment mistakenly block IP addresses ending in .0 and .255.

You can assign IP addresses from an IPAddressPool to services and namespaces by configuring the spec.serviceAllocation specification.

Table 2. MetalLB IPAddressPool custom resource spec.serviceAllocation subfields
Parameter Type Description

priority

int

Optional: Defines the priority between IP address pools when more than one IP address pool matches a service or namespace. A lower number indicates a higher priority.

namespaces

array (string)

Optional: Specifies a list of namespaces that you can assign to IP addresses in an IP address pool.

namespaceSelectors

array (LabelSelector)

Optional: Specifies namespace labels that you can assign to IP addresses from an IP address pool by using label selectors in a list format.

serviceSelectors

array (LabelSelector)

Optional: Specifies service labels that you can assign to IP addresses from an address pool by using label selectors in a list format.

Configuring an address pool

To precisely manage external access to application workloads, configure MetalLB address pools for your cluster. By defining these pools, you can control the specific IP address ranges assigned to load balancer services for consistent network routing.

Prerequisites

  • Install the OpenShift CLI (oc).

  • Log in as a user with cluster-admin privileges.

Procedure

  1. Create a file, such as ipaddresspool.yaml, with content like the following example:

    apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  namespace: metallb-system
  name: doc-example
  labels:
    zone: east
spec:
  addresses:
  - 203.0.113.1-203.0.113.10
  - 203.0.113.65-203.0.113.75
# ...

    where:

    labels

    The label assigned to the IPAddressPool can be referenced by the ipAddressPoolSelectors in the BGPAdvertisement CRD to associate the IPAddressPool with the advertisement.

  2. Apply the configuration for the IP address pool by entering the following command:

    $ oc apply -f ipaddresspool.yaml
Verification

  1. View the address pool by entering the following command:

    $ oc describe -n metallb-system IPAddressPool doc-example
    Example output
    Name:         doc-example
Namespace:    metallb-system
Labels:       zone=east
Annotations:  <none>
API Version:  metallb.io/v1beta1
Kind:         IPAddressPool
Metadata:
  ...
Spec:
  Addresses:
    203.0.113.1-203.0.113.10
    203.0.113.65-203.0.113.75
  Auto Assign:  true
Events:         <none>

  2. Confirm that the address pool name, such as doc-example, and the IP address ranges exist in the output.

Configure MetalLB address pool for VLAN

To precisely manage external access across a specific VLAN, configure MetalLB address pools for your cluster. Defining these pools ensures that load balancer services receive authorized IP addresses from designated network ranges for secure and consistent routing.

Prerequisites

  • Install the OpenShift CLI (oc).

  • Configure a separate VLAN.

  • Log in as a user with cluster-admin privileges.

Procedure

  1. Create a file, such as ipaddresspool-vlan.yaml, that is similar to the following example:

    apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  namespace: metallb-system
  name: doc-example-vlan
  labels:
    zone: east
spec:
  addresses:
  - 192.168.100.1-192.168.100.254
# ...

    where:

    labels.zone

    This label assigned to the IPAddressPool can be referenced by the ipAddressPoolSelectors in the BGPAdvertisement CRD to associate the IPAddressPool with the advertisement.

    spec.addresses

    This IP range must match the subnet assigned to the VLAN on your network. To support layer 2 (L2) mode, the IP address range must be within the same subnet as the cluster nodes.

  2. Apply the configuration for the IP address pool:

    $ oc apply -f ipaddresspool-vlan.yaml

  3. To ensure this configuration applies to the VLAN, you need to set the spec gatewayConfig.ipForwarding to Global.

    1. Run the following command to edit the network configuration custom resource (CR):

      $ oc edit network.operator.openshift/cluster

    2. Update the spec.defaultNetwork.ovnKubernetesConfig section to include the gatewayConfig.ipForwarding set to Global. The following example demonstrates this configuration:

      apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  clusterNetwork:
    - cidr: 10.128.0.0/14
      hostPrefix: 23
  defaultNetwork:
    type: OVNKubernetes
    ovnKubernetesConfig:
      gatewayConfig:
        ipForwarding: Global
# ...

Example address pool configurations

To precisely allocate IP address ranges for cluster services, configure MetalLB address pools by using Classless Inter-Domain Routing (CIDR) notation or hyphenated bounds. Defining these specific ranges ensures that application workloads receive valid IP assignments that align with your existing network infrastructure requirements.

Example of IPv4 and CIDR ranges

You can specify a range of IP addresses in classless inter-domain routing (CIDR) notation. You can combine CIDR notation with the notation that uses a hyphen to separate lower and upper bounds.

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: doc-example-cidr
  namespace: metallb-system
spec:
  addresses:
  - 192.168.100.0/24
  - 192.168.200.0/24
  - 192.168.255.1-192.168.255.5
# ...
Example of assigning IP addresses

You can set the autoAssign parameter to false to prevent MetalLB from automatically assigning IP addresses from the address pool. You can then assign a single IP address or multiple IP addresses from an IP address pool. To assign an IP address, append the /32 CIDR notation to the target IP address in the spec.addresses parameter. This setting ensures that only the specific IP address is available for assignment, leaving non-reserved IP addresses for application use.

Example IPAddressPool CR that assigns multiple IP addresses
apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: doc-example-reserved
  namespace: metallb-system
spec:
  addresses:
  - 192.168.100.1/32
  - 192.168.200.1/32
  autoAssign: false
# ...

When you add a service, you can request a specific IP address from the address pool or you can specify the pool name in an annotation to request any IP address from the pool.
Example of IPv4 and IPv6 addresses

You can add address pools that use IPv4 and IPv6. You can specify multiple ranges in the addresses list, just like several IPv4 examples.

How the service is assigned to a single IPv4 address, a single IPv6 address, or both is determined by how you add the service. The spec.ipFamilies and spec.ipFamilyPolicy parameters control how IP addresses are assigned to the service.

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: doc-example-combined
  namespace: metallb-system
spec:
  addresses:
  - 10.0.100.0/28
  - 2002:2:2::1-2002:2:2::100
# ...

spec.addresses: This list defines the IP ranges that MetalLB manages. This specific example is a dual-stack configuration, meaning it provides both IPv4 and IPv6 addresses.

Example of assigning IP address pools to services or namespaces

You can assign IP addresses from an IPAddressPool to services and namespaces that you specify.

If you assign a service or namespace to more than one IP address pool, MetalLB uses an available IP address from the higher-priority IP address pool. If no IP addresses are available from the assigned IP address pools with a high priority, MetalLB uses available IP addresses from an IP address pool with lower priority or no priority.

You can use the matchLabels label selector, the matchExpressions label selector, or both, for the namespaceSelectors and serviceSelectors specifications. This example demonstrates one label selector for each specification.

 
apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: doc-example-service-allocation
  namespace: metallb-system
spec:
  addresses:
    - 192.168.20.0/24
  serviceAllocation:
    priority: 50
    namespaces:
      - namespace-a
      - namespace-b
    namespaceSelectors:
      - matchLabels:
          zone: east
    serviceSelectors:
      - matchExpressions:
        - key: security
          operator: In
          values:
          - S1
# ...

where:

serviceAllocation.priority

Assign a priority to the address pool. A lower number indicates a higher priority.

serviceAllocation.namespaces

Assign one or more namespaces to the IP address pool in a list format.

serviceAllocation.namespaceSelectors

Assign one or more namespace labels to the IP address pool by using label selectors in a list format.

serviceAllocation.serviceSelectors

Assign one or more service labels to the IP address pool by using label selectors in a list format.

Additional resources