Advanced AddressPool configuration

Controlling automatic address allocation

In some environments, you’ll have some large address pools of “cheap” private IPs (e.g. RFC1918), and some smaller pools of “expensive” IPs (e.g. leased public IPv4 addresses).

By default, MetalLB will allocate IPs from any configured address pool with free addresses. This might end up using “expensive” addresses for services that don’t require it.

To prevent this behaviour you can disable automatic allocation for a pool by setting the autoAssign flag to false:

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

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: expensive
  namespace: metallb-system
spec:
  addresses:
  - 42.176.25.64/30
  autoAssign: false

Addresses can still be specifically allocated from the “expensive” pool with the methods described in the usage section.

Reduce scope of address allocation to specific Namespace and Service

This option can be used to reduce the scope of particular IPAddressPool to set of namespaces and services, by adding an optional namespace and/or service selectors. This is useful for mutitenant context in which there is a need for pinning IPAddressPool to specific namespace/service.

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: ippool-ns-service-alloc-sample
  namespace: metallb-system
spec:
  addresses:
    - 192.168.20.0/24
  avoidBuggyIPs: true
  serviceAllocation:
    priority: 50
    namespaces:
      - namespace-a
      - namespace-b
    namespaceSelectors:
      - matchLabels:
          foo: bar
    serviceSelectors:
      - matchExpressions:
          - {key: app, operator: In, values: [bar]}

The above IPAddressPool example is pinned to Service(s) which has a label matching with expression key: app, operator: In, values: [bar] created either in namespace-a or namespace-b or any namespace has a label foo:bar.

If multiple IPAddressPool objects are available to a Service, MetalLB will check for the availability of IPs by sorting the matching IPAddressPool objects by priority. It will first select the IPAddressPool with the lowest priority number (i.e., priority=1 is the highest priority). If the priority field is unset or set to 0, it will have the lowest priority (i.e., it will be the last pool to be used). If multiple IPAddressPool objects have the same priority, the choice will be random.

Handling buggy networks

Some old consumer network equipment mistakenly blocks IP addresses ending in .0 and .255, because of misguided smurf protection.

If you encounter this issue with your users or networks, you can set the AvoidBuggyIPs flag of the IPAddressPool CR. By doing so, the .0 and the .255 addresses will be avoided.

Changing the IP of a service

The current behaviour of MetalLB is to try to preserve the connectivity despite a change of configuration that might disrupt a service happens. For example, removing an IPAddressPool that contains IPs currently assigned to services.

If that happens, instead of reallocating (if possible) a new IP to the service, the configuration change is marked as stale and MetalLB keeps running with the last valid configuration.

In order to re-assign a new IP to the services, there are two options:

• restarting the MetalLB’s controller pod
• deleting and re-creating the service