Configuring MetalLB address pools - Load balancing with MetalLB | Networking

About the IPAddressPool custom resource
Configuring an address pool
Example address pool configurations
Additional resources
Next steps

As a cluster administrator, you can add, modify, and delete address pools. The MetalLB Operator uses the address pool custom resources to set the IP addresses that MetalLB can assign to services. The namespace used in the examples assume the namespace is metallb-system.

About the IPAddressPool custom resource

The fields for the IPAddressPool custom resource are described in the following tables.

Table 1. MetalLB IPAddressPool pool custom resource
Field	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.universe.tf/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 MetalLB Operator to assign to services. You can specify multiple ranges in a single pool; they will all share the same settings. Specify each range in CIDR notation or as starting and ending IP addresses separated with a hyphen.
`spec.autoAssign`	`boolean`	Optional: Specifies whether MetalLB automatically assigns IP addresses from this pool. Specify `false` if you want explicitly request an IP address from this pool with the `metallb.universe.tf/address-pool` annotation. The default value is `true`.
`spec.avoidBuggyIPs`	`boolean`	Optional: This ensures when enabled that 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
Field	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

As a cluster administrator, you can add address pools to your cluster to control the IP addresses that MetalLB can assign to load-balancer services.

Prerequisites

Install the OpenShift CLI (oc).
Log in as a user with cluster-admin privileges.

Procedure

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: (1)
    zone: east
spec:
  addresses:
  - 203.0.113.1-203.0.113.10
  - 203.0.113.65-203.0.113.75

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

Apply the configuration for the IP address pool:
```
$ oc apply -f ipaddresspool.yaml
```

Verification

View the address pool:

$ 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>

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

Example address pool configurations

Example: IPv4 and CIDR ranges

You can specify a range of IP addresses in 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: Reserve IP addresses

You can set the autoAssign field to false to prevent MetalLB from automatically assigning the IP addresses from the pool. When you add a service, you can request a specific IP address from the pool or you can specify the pool name in an annotation to request any IP address from the pool.

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: doc-example-reserved
  namespace: metallb-system
spec:
  addresses:
  - 10.0.100.0/28
  autoAssign: false

Example: 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.

Whether the service is assigned a single IPv4 address, a single IPv6 address, or both is determined by how you add the service. The spec.ipFamilies and spec.ipFamilyPolicy fields 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

Example: Assign 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 (1)
    namespaces: (2)
      - namespace-a
      - namespace-b
    namespaceSelectors: (3)
      - matchLabels:
          zone: east
    serviceSelectors: (4)
      - matchExpressions:
        - key: security
          operator: In
          values:
          - S1

1	Assign a priority to the address pool. A lower number indicates a higher priority.
2	Assign one or more namespaces to the IP address pool in a list format.
3	Assign one or more namespace labels to the IP address pool by using label selectors in a list format.
4	Assign one or more service labels to the IP address pool by using label selectors in a list format.

Additional resources

Configuring MetalLB with an L2 advertisement and label.

Next steps

For BGP mode, see Configuring MetalLB BGP peers.
Configuring services to use MetalLB.