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Chapter 4. Enabling multicast for a project

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

Important

At this time, multicast is best used for low-bandwidth coordination or service discovery and not a high-bandwidth solution.
By default, network policies affect all connections in a namespace. However, multicast is unaffected by network policies. If multicast is enabled in the same namespace as your network policies, it is always allowed, even if there is a deny-all network policy. Cluster administrators should consider the implications to the exemption of multicast from network policies before enabling it.

Multicast traffic between OpenShift Dedicated pods is disabled by default. If you are using the OVN-Kubernetes network plugin, you can enable multicast on a per-project basis.

4.2. Enabling multicast between pods
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You can enable multicast between pods for your project.

Prerequisites

Install the OpenShift CLI (oc).
You must log in to the cluster with a user that has the cluster-admin or the dedicated-admin role.

Procedure

Run the following command to enable multicast for a project. Replace <namespace> with the namespace for the project you want to enable multicast for.

oc annotate namespace <namespace> \
    k8s.ovn.org/multicast-enabled=true

$ oc annotate namespace <namespace> \
    k8s.ovn.org/multicast-enabled=true

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Tip

You can alternatively apply the following YAML to add the annotation:

apiVersion: v1
kind: Namespace
metadata:
  name: <namespace>
  annotations:
    k8s.ovn.org/multicast-enabled: "true"

apiVersion: v1
kind: Namespace
metadata:
  name: <namespace>
  annotations:
    k8s.ovn.org/multicast-enabled: "true"

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Verification

To verify that multicast is enabled for a project, complete the following procedure:

Change your current project to the project that you enabled multicast for. Replace <project> with the project name.
```
oc project <project>
```
```
$ oc project <project>
```
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Create a pod to act as a multicast receiver:

cat <<EOF| oc create -f -
apiVersion: v1
kind: Pod
metadata:
  name: mlistener
  labels:
    app: multicast-verify
spec:
  containers:
    - name: mlistener
      image: registry.access.redhat.com/ubi9
      command: ["/bin/sh", "-c"]
      args:
        ["dnf -y install socat hostname && sleep inf"]
      ports:
        - containerPort: 30102
          name: mlistener
          protocol: UDP
EOF

$ cat <<EOF| oc create -f -
apiVersion: v1
kind: Pod
metadata:
  name: mlistener
  labels:
    app: multicast-verify
spec:
  containers:
    - name: mlistener
      image: registry.access.redhat.com/ubi9
      command: ["/bin/sh", "-c"]
      args:
        ["dnf -y install socat hostname && sleep inf"]
      ports:
        - containerPort: 30102
          name: mlistener
          protocol: UDP
EOF

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Create a pod to act as a multicast sender:

cat <<EOF| oc create -f -
apiVersion: v1
kind: Pod
metadata:
  name: msender
  labels:
    app: multicast-verify
spec:
  containers:
    - name: msender
      image: registry.access.redhat.com/ubi9
      command: ["/bin/sh", "-c"]
      args:
        ["dnf -y install socat && sleep inf"]
EOF

$ cat <<EOF| oc create -f -
apiVersion: v1
kind: Pod
metadata:
  name: msender
  labels:
    app: multicast-verify
spec:
  containers:
    - name: msender
      image: registry.access.redhat.com/ubi9
      command: ["/bin/sh", "-c"]
      args:
        ["dnf -y install socat && sleep inf"]
EOF

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In a new terminal window or tab, start the multicast listener.

Get the IP address for the Pod:

POD_IP=$(oc get pods mlistener -o jsonpath='{.status.podIP}')

$ POD_IP=$(oc get pods mlistener -o jsonpath='{.status.podIP}')

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Start the multicast listener by entering the following command:

oc exec mlistener -i -t -- \
    socat UDP4-RECVFROM:30102,ip-add-membership=224.1.0.1:$POD_IP,fork EXEC:hostname

$ oc exec mlistener -i -t -- \
    socat UDP4-RECVFROM:30102,ip-add-membership=224.1.0.1:$POD_IP,fork EXEC:hostname

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Start the multicast transmitter.

Get the pod network IP address range:

CIDR=$(oc get Network.config.openshift.io cluster \
    -o jsonpath='{.status.clusterNetwork[0].cidr}')

$ CIDR=$(oc get Network.config.openshift.io cluster \
    -o jsonpath='{.status.clusterNetwork[0].cidr}')

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To send a multicast message, enter the following command:

oc exec msender -i -t -- \
    /bin/bash -c "echo | socat STDIO UDP4-DATAGRAM:224.1.0.1:30102,range=$CIDR,ip-multicast-ttl=64"

$ oc exec msender -i -t -- \
    /bin/bash -c "echo | socat STDIO UDP4-DATAGRAM:224.1.0.1:30102,range=$CIDR,ip-multicast-ttl=64"

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If multicast is working, the previous command returns the following output:

mlistener

mlistener

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Chapter 4. Enabling multicast for a project

4.1. About multicast
링크 복사

4.2. Enabling multicast between pods
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Chapter 4. Enabling multicast for a project

4.1. About multicast링크 복사링크가 클립보드에 복사되었습니다!

4.2. Enabling multicast between pods링크 복사링크가 클립보드에 복사되었습니다!

자세한 정보

평가판, 구매 및 판매

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Red Hat 문서 정보

보다 포괄적 수용을 위한 오픈 소스 용어 교체

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4.1. About multicast
링크 복사

4.2. Enabling multicast between pods
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