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Multus CNI usage guide

Prerequisites

  • Kubelet configured to use CNI
  • Kubernetes version with CRD support (generally )

Your Kubelet(s) must be configured to run with the CNI network plugin. Please see Kubernetes document for CNI for more details.

Install Multus

Generally we recommend two options: Manually place a Multus binary in your /opt/cni/bin, or use our quick-start method -- which creates a daemonset that has an opinionated way of how to install & configure Multus CNI (recommended).

Copy Multus Binary into place

You may acquire the Multus binary via compilation (see the developer guide) or download the a binary from the GitHub releases page. Copy multus binary into CNI binary directory, usually /opt/cni/bin. Perform this on all nodes in your cluster (master and nodes).

cp multus /opt/cni/bin

Via Daemonset method

As a quickstart, you may apply these YAML files (included in the clone of this repository). Run this command (typically you would run this on the master, or wherever you have access to the kubectl command to manage your cluster).

cat ./deployments/multus-daemonset.yml | kubectl apply -f -  # thin deployment

or

cat ./deployments/multus-daemonset-thick.yml | kubectl apply -f - # thick (client/server) deployment

If you need more comprehensive detail, continue along with this guide, otherwise, you may wish to either follow the quickstart guide or skip to the 'Create network attachment definition' section.

Set up conf file in /etc/cni/net.d/ (Installed automatically by Daemonset)

If you use daemonset to install multus, skip this section and go to "Create network attachment"

You put CNI config file in /etc/cni/net.d. Kubernetes CNI runtime uses the alphabetically first file in the directory. ("NOTE1", "NOTE2" are just comments, you can remove them at your configuration)

Execute following commands at all Kubernetes nodes (i.e. master and minions)

mkdir -p /etc/cni/net.d
cat >/etc/cni/net.d/00-multus.conf <<EOF
{
  "name": "multus-cni-network",
  "type": "multus",
  "readinessindicatorfile": "/run/flannel/subnet.env",
  "delegates": [
    {
      "NOTE1": "This is example, wrote your CNI config in delegates",
      "NOTE2": "If you use flannel, you also need to run flannel daemonset before!",
      "type": "flannel",
      "name": "flannel.1",
      "delegate": {
        "isDefaultGateway": true
      }
    }
  ],
  "kubeconfig": "/etc/cni/net.d/multus.d/multus.kubeconfig"
}
EOF

For the detail, please take a look into Configuration Reference

NOTE: You can use "clusterNetwork"/"defaultNetworks" instead of "delegates", see for the detail

As above config, you need to set "kubeconfig" in the config file for NetworkAttachmentDefinition(CRD).

Which network will be used for "Pod IP"?

In case of "delegates", the first delegates network will be used for "Pod IP". Otherwise, "clusterNetwork" will be used for "Pod IP".

Create ServiceAccount, ClusterRole and its binding

Create resources for multus to access CRD objects as following command:

# Execute following commands at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: v1
kind: ServiceAccount
metadata:
  name: multus
  namespace: kube-system
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: multus
rules:
  - apiGroups: ["k8s.cni.cncf.io"]
    resources:
      - '*'
    verbs:
      - '*'
  - apiGroups:
      - ""
    resources:
      - pods
      - pods/status
    verbs:
      - get
      - update
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: multus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: multus
subjects:
- kind: ServiceAccount
  name: multus
  namespace: kube-system
EOF

Set up kubeconfig file

Create kubeconfig at master node as following commands:

# Execute following command at Kubernetes master
mkdir -p /etc/cni/net.d/multus.d
SERVICEACCOUNT_CA=$(kubectl get secrets -n=kube-system -o json | jq -r '.items[]|select(.metadata.annotations."kubernetes.io/service-account.name"=="multus")| .data."ca.crt"')
SERVICEACCOUNT_TOKEN=$(kubectl get secrets -n=kube-system -o json | jq -r '.items[]|select(.metadata.annotations."kubernetes.io/service-account.name"=="multus")| .data.token' | base64 -d )
KUBERNETES_SERVICE_PROTO=$(kubectl get all -o json | jq -r .items[0].spec.ports[0].name)
KUBERNETES_SERVICE_HOST=$(kubectl get all -o json | jq -r .items[0].spec.clusterIP)
KUBERNETES_SERVICE_PORT=$(kubectl get all -o json | jq -r .items[0].spec.ports[0].port)
cat > /etc/cni/net.d/multus.d/multus.kubeconfig <<EOF
# Kubeconfig file for Multus CNI plugin.
apiVersion: v1
kind: Config
clusters:
- name: local
  cluster:
    server: ${KUBERNETES_SERVICE_PROTOCOL:-https}://${KUBERNETES_SERVICE_HOST}:${KUBERNETES_SERVICE_PORT}
    certificate-authority-data: ${SERVICEACCOUNT_CA}
users:
- name: multus
  user:
    token: "${SERVICEACCOUNT_TOKEN}"
contexts:
- name: multus-context
  context:
    cluster: local
    user: multus
current-context: multus-context
EOF

Copy /etc/cni/net.d/multus.d/multus.kubeconfig into other Kubernetes nodes NOTE: Recommend to exec 'chmod 600 /etc/cni/net.d/multus.d/multus.kubeconfig' to keep secure

scp /etc/cni/net.d/multus.d/multus.kubeconfig ...

Setup CRDs (daemonset automatically does)

If you use daemonset to install multus, skip this section and go to "Create network attachment"

Create CRD definition in Kubernetes as following command at master node:

# Execute following command at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: apiextensions.k8s.io/v1beta1
kind: CustomResourceDefinition
metadata:
  name: network-attachment-definitions.k8s.cni.cncf.io
spec:
  group: k8s.cni.cncf.io
  version: v1
  scope: Namespaced
  names:
    plural: network-attachment-definitions
    singular: network-attachment-definition
    kind: NetworkAttachmentDefinition
    shortNames:
    - net-attach-def
  validation:
    openAPIV3Schema:
      properties:
        spec:
          properties:
            config:
                 type: string
EOF

Create network attachment definition

The 'NetworkAttachmentDefinition' is used to setup the network attachment, i.e. secondary interface for the pod, There are two ways to configure the 'NetworkAttachmentDefinition' as following:

  • NetworkAttachmentDefinition with json CNI config
  • NetworkAttachmentDefinition with CNI config file

NetworkAttachmentDefinition with json CNI config:

Following command creates NetworkAttachmentDefinition. CNI config is in config: field.

# Execute following command at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: macvlan-conf-1
spec:
  config: '{
            "cniVersion": "0.3.0",
            "type": "macvlan",
            "master": "eth1",
            "mode": "bridge",
            "ipam": {
                "type": "host-local",
                "ranges": [
                    [ {
                         "subnet": "10.10.0.0/16",
                         "rangeStart": "10.10.1.20",
                         "rangeEnd": "10.10.3.50",
                         "gateway": "10.10.0.254"
                    } ]
                ]
            }
        }'
EOF

NetworkAttachmentDefinition with CNI config file:

If NetworkAttachmentDefinition has no spec, multus find a file in defaultConfDir ('/etc/cni/multus/net.d', with same name in the 'name' field of CNI config.

# Execute following command at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: macvlan-conf-2
EOF

# Execute following commands at all Kubernetes nodes (i.e. master and minions)
cat <<EOF > /etc/cni/multus/net.d/macvlan2.conf
{
  "cniVersion": "0.3.0",
  "type": "macvlan",
  "name": "macvlan-conf-2",
  "master": "eth1",
  "mode": "bridge",
  "ipam": {
      "type": "host-local",
      "ranges": [
          [ {
               "subnet": "11.10.0.0/16",
               "rangeStart": "11.10.1.20",
               "rangeEnd": "11.10.3.50"
          } ]
      ]
  }
}
EOF

Run pod with network annotation

Launch pod with text annotation

# Execute following command at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: pod-case-01
  annotations:
    k8s.v1.cni.cncf.io/networks: macvlan-conf-1, macvlan-conf-2
spec:
  containers:
  - name: pod-case-01
    image: docker.io/centos/tools:latest
    command:
    - /sbin/init
EOF

Launch pod with text annotation for NetworkAttachmentDefinition in different namespace

You can also specify NetworkAttachmentDefinition with its namespace as adding <namespace>/

# Execute following command at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: macvlan-conf-3
  namespace: testns1
spec:
  config: '{
            "cniVersion": "0.3.0",
            "type": "macvlan",
            "master": "eth1",
            "mode": "bridge",
            "ipam": {
                "type": "host-local",
                "ranges": [
                    [ {
                         "subnet": "12.10.0.0/16",
                         "rangeStart": "12.10.1.20",
                         "rangeEnd": "12.10.3.50"
                    } ]
                ]
            }
        }'
EOF
cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: pod-case-02
  annotations:
    k8s.v1.cni.cncf.io/networks: testns1/macvlan-conf-3
spec:
  containers:
  - name: pod-case-02
    image: docker.io/centos/tools:latest
    command:
    - /sbin/init
EOF

Launch pod with text annotation with interface name

You can also specify interface name as adding @<ifname>.

# Execute following command at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: pod-case-03
  annotations:
    k8s.v1.cni.cncf.io/networks: macvlan-conf-1@macvlan1
spec:
  containers:
  - name: pod-case-03
    image: docker.io/centos/tools:latest
    command:
    - /sbin/init
EOF

Launch pod with json annotation

# Execute following command at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: pod-case-04
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
            { "name" : "macvlan-conf-1" },
            { "name" : "macvlan-conf-2" }
    ]'
spec:
  containers:
  - name: pod-case-04
    image: docker.io/centos/tools:latest
    command:
    - /sbin/init
EOF

Launch pod with json annotation for NetworkAttachmentDefinition in different namespace

You can also specify NetworkAttachmentDefinition with its namespace as adding "namespace": "<namespace>".

# Execute following command at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: pod-case-05
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
            { "name" : "macvlan-conf-1",
              "namespace": "testns1" }
    ]'
spec:
  containers:
  - name: pod-case-05
    image: docker.io/centos/tools:latest
    command:
    - /sbin/init
EOF

Launch pod with json annotation with interface

You can also specify interface name as adding "interface": "<ifname>".

# Execute following command at Kubernetes master
cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: pod-case-06
  annotations:
    k8s.v1.cni.cncf.io/networks: '[
            { "name" : "macvlan-conf-1",
              "interface": "macvlan1" },
            { "name" : "macvlan-conf-2" }
    ]'
spec:
  containers:
  - name: pod-case-06
    image: docker.io/centos/tools:latest
    command:
    - /sbin/init
EOF

Verifying pod network

Following the example of ip -d address output of above pod, "pod-case-06":

# Execute following command at Kubernetes master
kubectl exec -it pod-case-06 -- ip -d address

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 promiscuity 0 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
3: eth0@if11: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UP group default
    link/ether 0a:58:0a:f4:02:06 brd ff:ff:ff:ff:ff:ff link-netnsid 0 promiscuity 0
    veth numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
    inet 10.244.2.6/24 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::ac66:45ff:fe7c:3a19/64 scope link
       valid_lft forever preferred_lft forever
4: macvlan1@if3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether 4e:6d:7a:4e:14:87 brd ff:ff:ff:ff:ff:ff link-netnsid 0 promiscuity 0
    macvlan mode bridge numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
    inet 10.10.1.22/16 scope global macvlan1
       valid_lft forever preferred_lft forever
    inet6 fe80::4c6d:7aff:fe4e:1487/64 scope link
       valid_lft forever preferred_lft forever
5: net2@if3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether 6e:e3:71:7f:86:f7 brd ff:ff:ff:ff:ff:ff link-netnsid 0 promiscuity 0
    macvlan mode bridge numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
    inet 11.10.1.22/16 scope global net2
       valid_lft forever preferred_lft forever
    inet6 fe80::6ce3:71ff:fe7f:86f7/64 scope link
       valid_lft forever preferred_lft forever
Interface name Description
lo loopback
eth0 Default network interface (flannel)
macvlan1 macvlan interface (macvlan-conf-1)
net2 macvlan interface (macvlan-conf-2)

Specifying a default route for a specific attachment

Typically, the default route for a pod will route traffic over the eth0 and therefore over the cluster-wide default network. You may wish to specify that a different network attachment will have the default route.

You can achieve this by using the JSON formatted annotation and specifying a default-route key.

NOTE: It's important that you consider that this may impact some functionality of getting traffic to route over the cluster-wide default network.

For example, we have a this configuration for macvlan:

cat <<EOF | kubectl create -f -
apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: macvlan-conf
spec:
  config: '{
      "cniVersion": "0.3.0",
      "type": "macvlan",
      "master": "eth0",
      "mode": "bridge",
      "ipam": {
        "type": "host-local",
        "subnet": "192.168.2.0/24",
        "rangeStart": "192.168.2.200",
        "rangeEnd": "192.168.2.216",
        "routes": [
          { "dst": "0.0.0.0/0" }
        ],
        "gateway": "192.168.2.1"
      }
    }'
EOF

We can then create a pod which uses the default-route key in the JSON formatted k8s.v1.cni.cncf.io/networks annotation.

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: samplepod
  annotations:
    k8s.v1.cni.cncf.io/networks: '[{
      "name": "macvlan-conf",
      "default-route": ["192.168.2.1"]
    }]'
spec:
  containers:
  - name: samplepod
    command: ["/bin/bash", "-c", "trap : TERM INT; sleep infinity & wait"]
    image: dougbtv/centos-network
EOF

This will set 192.168.2.1 as the default route over the net1 interface, such as:

kubectl exec -it samplepod -- ip route

default via 192.168.2.1 dev net1 
10.244.0.0/24 dev eth0  proto kernel  scope link  src 10.244.0.169 
10.244.0.0/16 via 10.244.0.1 dev eth0

Entrypoint Parameters

Multus CNI, when installed using the daemonset-style installation uses an entrypoint script which copies the Multus binary into place, places CNI configurations. This entrypoint takes a variety of parameters for customization.

Typically, you'd modified the daemonset YAML itself to specify these parameters.

For example, the command and args parameters in the containers section of the DaemonSet may look something like:

  command: ["/entrypoint.sh"]
  args:
  - "--multus-conf-file=auto"
  - "--namespace-isolation=true"
  - "--multus-log-level=verbose"

Note that some of the defaults have directories inside the root directory named /host/, this is because it is deployed as a container and we have host file system locations mapped into this directory inside the container. If you use other directories, you may have to change the mounted volumes.

Entrypoint script parameters

Each parameter is shown with the default as the value.

--cni-conf-dir=/host/etc/cni/net.d

This is the configuration directory where Multus will write its configuration file.

--cni-bin-dir=/host/opt/cni/bin

This the directory in which the Multus binary will be installed.

--namespace-isolation=false

Setting this option to true enables the Namespace isolation feature, which insists that custom resources must be created in the same namespace as the pods, otherwise it will refuse to attach those definitions as additional interfaces. See (the configuration guide for more information)[configuration.md].

--global-namespaces=default,foo,bar

The --global-namespaces works only when --namespace-isolation=true. This takes a comma-separated list of namespaces which can be referred to globally when namespace isolation is enabled. See (the configuration guide for more information)[configuration.md].

--multus-bin-file=/usr/src/multus-cni/bin/multus

This option lets you set which binary executable to copy from the container onto the host (into the directory specified by --cni-bin-dir), allowing one to copy an alternate version or build of Multus CNI.

--multus-conf-file=/usr/src/multus-cni/images/70-multus.conf

The --multus-conf-file is one of two options; it can be set to a source file to be copied into the location specified by --cni-conf-dir. Or, to a value of auto, that is: --multus-conf-file=auto.

The automatic configuration option is used to automatically generate Multus configurations given existing on-disk CNI configurations for your default network.

In the case that --multus-conf-file=auto -- The entrypoint script will look at the --multus-autoconfig-dir (by default, the same as the --cni-conf-dir). Multus will wait (600 seconds) until there's a CNI configuration file there, and it will take the alphabetically first configuration there, and it will wrap that configuration into a Multus configuration.

--multus-autoconfig-dir=/host/etc/cni/net.d

Used only with --multus-conf-file=auto. This option allows one to set which directory will be used to generate configuration files.

This can be used if you have your CNI configuration stored in an alternate location, or, you have constraints on race conditions where you'd like to generate your default network configuration first, and then only have Multus write its configuration when it finds that configuration -- allowing only Multus to write the CNI configuration in the --cni-conf-dir, therefore notifying the Kubelet that the node is in a ready state.

--multus-kubeconfig-file-host=/etc/cni/net.d/multus.d/multus.kubeconfig

Used only with --multus-conf-file=auto. Allows you to specify an alternate path to the Kubeconfig.

--multus-master-cni-file-name=

The --multus-master-cni-file-name can be used to select the cni file as the master cni, rather than the first file in cni-conf-dir. For example, --multus-master-cni-file-name=10-calico.conflist.

--multus-log-level=
--multus-log-file=

Used only with --multus-conf-file=auto. See the documentation for logging for which values are permitted.

Used only with --multus-conf-file=auto. Allows you to specify CNI spec version. Please set if you need to specify CNI spec version.

--cni-version=

In some cases, the original CNI configuration that the Multus configuration was generated from (using --multus-conf-file=auto) may be used as a sort of semaphor for network readiness -- as this model is used by the Kubelet itself. If you need to disable Multus' availability, you may wish to clean out the generated configuration file when the source file for autogeneration of the config file is no longer present. You can use this functionality by setting:

--cleanup-config-on-exit=true

Additionally when using CRIO, you may wish to have the CNI config file that's used as the source for --multus-conf-file=auto renamed. This boolean option when set to true automatically renames the file with a .old suffix to the original filename.

--rename-conf-file=true

When using --multus-conf-file=auto you may also care to specify a binDir in the configuration, this can be accomplished using the --additional-bin-dir option.

--additional-bin-dir=/opt/multus/bin

Sometimes, you may wish to not have the entrypoint copy the binary file onto the host. Potentially, you have another way to copy in a specific version of Multus, for example. By default, it's always copied, but you may disable the copy with:

--skip-multus-binary-copy=true

If you wish to have auto configuration use the readinessindicatorfile in the configuration, you can use the --readiness-indicator-file to express which file should be used as the readiness indicator.

--readiness-indicator-file=/path/to/file