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Version: 3.18 (latest)

Restrict a pod to use an IP address in a specific range

Big picture

Restrict the IP address chosen for a pod to a specific range of IP addresses.

Value

When Kubernetes pods interact with external systems that make decisions based on IP ranges (for example legacy firewalls), it can be useful to define several IP ranges and explicitly assign pods to those ranges. Using Calico Enterprise IP Address Management (IPAM), you can restrict a pod to use an address from within a specific range.

Features

This how-to guide uses the following features:

  • Calico Enterprise IPAM
  • IPPool resource

Concepts

Kubernetes pod CIDR

The Kubernetes pod CIDR is the range of IPs Kubernetes expects pod IPs to be assigned from. It is defined for the entire cluster and is used by various Kubernetes components to determine whether an IP belongs to a pod. For example, kube-proxy treats traffic differently if that traffic is from a pod than if it is not. All pod IPs must be in the CIDR range for Kubernetes to function correctly.

IP Pool

IP pools are ranges of IP addresses from which Calico Enterprise assigns pod IPs. By default, Calico Enterprise creates an IP pool for the entire Kubernetes pod CIDR, but you can change this to break the pod CIDR up into several pools. You can control which pool Calico Enterprise uses for each pod using node selectors, or annotations on the pod or the pod’s namespace.

Before you begin...

The features in this How to guide require:

  • Calico Enterprise IPAM

If you are not sure which IPAM your cluster is using, the way to tell depends on install method.

The IPAM plugin can be queried on the default Installation resource.

kubectl get installation default -o go-template --template {{.spec.cni.ipam.type}}

If your cluster is using Calico IPAM, the above command should return a result of Calico.

Additionally, cluster administrators must have configured IP pools to define the valid IP ranges to use for allocating pod IP addresses.

How to

Restrict a pod to use an IP address range

Annotate the pod with key cni.projectcalico.org/ipv4pools and/or cni.projectcalico.org/ipv6pools and value set to a list of IP pool names, enclosed in brackets. For example:

cni.projectcalico.org/ipv4pools: '["pool-1", "pool-2"]'

Note the use of the escaped \" for the inner double quotes around the pool names.

Restrict all pods within a namespace to use an IP address range

Annotate the namespace with key cni.projectcalico.org/ipv4pools and/or cni.projectcalico.org/ipv6pools and value set to a list of IP pool names, enclosed in brackets. For example:

cni.projectcalico.org/ipv4pools: '["pool-1", "pool-2"]'

Note the use of the escaped \" for the inner double quotes around the pool names.

If both the pod and the pod’s namespace have the annotation, the pod annotation takes precedence.

The annotation must be present at the time the pod is created. Adding it to an existing pod has no effect.

Additional resources

For help configuring Calico Enterprise IPAM, see Configuring the Calico Enterprise CNI Plugins.