About multicast

With IP multicast, data is broadcast to many IP addresses simultaneously.

At this time, multicast is best used for low-bandwidth coordination or service discovery and not a high-bandwidth solution.

Multicast traffic between OpenShift Container Platform Pods is disabled by default. If you are using the OpenShift SDN network plug-in, you can enable multicast on a per-project basis.

When using the OpenShift SDN network plug-in in networkpolicy isolation mode:

  • Multicast packets sent by a Pod will be delivered to all other Pods in the project, regardless of NetworkPolicy objects. Pods might be able to communicate over multicast even when they cannot communicate over unicast.

  • Multicast packets sent by a Pod in one project will never be delivered to Pods in any other project, even if there are NetworkPolicy objects that allow communication between the projects.

When using the OpenShift SDN network plug-in in multitenant isolation mode:

  • Multicast packets sent by a Pod will be delivered to all other Pods in the project.

  • Multicast packets sent by a Pod in one project will be delivered to Pods in other projects only if each project is joined together and multicast is enabled in each joined project.

Enabling multicast between Pods

You can enable multicast between Pods for your project.

Prerequisites
  • Install the OpenShift Command-line Interface (CLI), commonly known as oc.

  • You must log in to the cluster with a user that has the cluster-admin role.

Procedure
  • Run the following command to enable multicast for a project:

    $ oc annotate netnamespace <namespace> \ (1)
        netnamespace.network.openshift.io/multicast-enabled=true
    1 The namespace for the project you want to enable multicast for.

Disabling multicast between Pods

You can disable multicast between Pods for your project.

Prerequisites
  • Install the OpenShift Command-line Interface (CLI), commonly known as oc.

  • You must log in to the cluster with a user that has the cluster-admin role.

Procedure
  • Disable multicast by running the following command:

    $ oc annotate netnamespace <namespace> \ (1)
        netnamespace.network.openshift.io/multicast-enabled-
    1 The namespace for the project you want to disable multicast for.