Kubernetes cluster network policies

Kubernetes network policies help configure network interchanges between groups of pods and network nodes. You can create network policies using the Kubernetes Network Policy API that sets rules for filtering traffic at the pod level. These rules determine which pods and services in a Kubernetes cluster can access each other.

To manage network policies, Managed Service for Kubernetes uses the Calico and Cilium controllers.

The Calico network controller uses the iptables rules while Cilium utilizes the eBPF technology.

Integration with load balancersIntegration with load balancers

For step-by-step instructions on how to set up access to an application using NetworkPolicy, see Granting access to an app running in a Kubernetes cluster.

CalicoCalico

Calico enables you to configure basic security policies for Kubernetes clusters.

Step-by-step configuration instructions are provided at Configuring the Calico network policy controller.

CiliumCilium

Unlike Calico, the Cilium controller has broader capabilities and enables you to:

• Use the same subnet ranges for pods and services in different clusters.
• Create more functional network policies, for example, by filtering pod-to-pod traffic at the L7 application layer or using the DNS name of an external resource.
• Use the built-in Hubble tool to monitor network events.

In a Managed Service for Kubernetes cluster, Cilium operates in tunneling mode. This mode implements network connectivity for cluster objects based on VxLAN technology using Cilium CNI.

Cilium tunneling mode helps:

• Create clusters with overlapping IP addresses on the same network.
• Use an extended address range of up to /8 for pod and cluster services.
• Create twice as many cluster nodes (as compared to Calico).

To be able to use tunnel mode, a service account requires the k8s.tunnelClusters.agent role.

Allow-all and deny-all network policiesAllow-all and deny-all network policies

Policies for incoming connectionsPolicies for incoming connections

You can create a policy that allows all incoming connections to all pods in a namespace. If such a policy is present, no other policy can ban incoming connections to these pods.

Example:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-all-ingress
spec:
  podSelector: {}
  ingress:
  - {}
  policyTypes:
  - Ingress

You can create a policy that bans all incoming connections to all pods in a namespace. Such policy ensures that all incoming connections will be banned for pods not selected by any other network policy.

Example:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-ingress
spec:
  podSelector: {}
  policyTypes:
  - Ingress

Policies for outgoing connectionsPolicies for outgoing connections

You can create a policy that allows all outgoing connections from all pods in a namespace. If such a policy is present, no other policy can ban incoming connections to these pods.

Example:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-all-egress
spec:
  podSelector: {}
  egress:
  - {}
  policyTypes:
  - Egress

You can create a policy that bans all outgoing connections from all pods in a namespace. Such policy ensures that all outgoing connections will be banned for pods not selected by any other network policy.

Example:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-egress
spec:
  podSelector: {}
  policyTypes:
  - Egress

For more information about NetworkPolicy, see resource fields and annotations.

Cluster requirements to enable network policiesCluster requirements to enable network policies

To enable network policies in a Kubernetes cluster, sufficient resources in node groups are required. Using network policies requires additional memory and vCPU resources.

We recommend that you only enable your network policy controller in a cluster of at least two nodes.