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Flannel

Flannel is a network layer, layer three, fabric for Kubernetes. It is designed to work with Linux routing infrastructure and creates a virtual network that gives each computing host a subnet. Flannel uses either the Kubernetes API or etcd directly to store the network configuration, the allocated subnets, and any auxiliary data such as the host’s public IP address. To learn more about Flannel, refer to the official documentation.

The Flannel pack includes the Container Network Interface (CNI) plugins required use Flannel in your cluster.

Versions Supported​

Prerequisites​

  • Kubernetes version 1.22 or later.

  • Existing cluster profiles that use Flannel version 0.21.x or earlier cannot upgrade to Flannel version 0.23.x. You must create a new cluster profile to use Flannel version 0.23.x. All Flannel versions 0.21.x and earlier are manifest based. The newer versions are pack based with additional logic that builds on top of the Helm chart.

Parameters​

The following table lists commonly used parameters for Flannel version 0.23.x. Refer to the pack YAML file for the complete list of parameters.

ParameterDescriptionDefault
pack.namespaceThe namespace to install Flannel. If the namespace does not exist, it will be created.kube-system
charts.flannel.podCidrThe IPv4 CIDR range to assign to the pod network. This should match the Kubernetes PodCIDR.192.168.0.0/16
charts.flannel.podCidrv6The IPv6 CIDR range to assign to the service network.""
charts.flannel.backendThe backend to use for Flannel. Refer to the official backend documentation to learn more about supported backends.vxlan
charts.flannel.image_cni.repositoryThe Flannel CNI image repository.docker.io/flannel/flannel-cni-plugin
charts.flannel.image_cni.tagThe Flannel CNI image tag.v1.1.2
charts.flannel.argsAdditional arguments to pass to the Flannel daemon. Refer to the key command line options documentation for a list of supported values.["--ip-masq","--kube-subnet-mgr"]

Usage​

Change the Backend​

If you need to change the backend type or update the backend port due to firewall or other restrictions, you can do so by updating the pack YAML. The parameters charts.flannel.backend and charts.flannel.backendPort can be used to change the default behavior. Refer to the official backend documentation to learn more about supported backends.

charts:
  flannel:
    backend: "vxlan"
    backendPort: 8472

Change MTU​

By default, Flannel will use the Maximum Transmission Unit (MTU) of the host interface. If you need to change the MTU, you can do so by updating the pack YAML. The parameter charts.flannel.mtu can be used to change the MTU value.

charts:
  flannel:
    mtu: 1500

VXLAN Configuration​

Additional parameters can be used to configure the VXLAN backend. The VXLAN configuration is commented out by default in the pack YAML. Uncomment the parameters you want to use and update the values as needed. Refer to the VXLAN backend documentation for additional guidance.

charts:
  flannel:
  VXLAN Configs:
    #VXLAN Identifier to be used. On Linux default is 1.
    vni: 1
    #Enable VXLAN Group Based Policy (Default false)
    GBP: false
    #Enable direct routes (default is false)
    directRouting: false
    #MAC prefix to be used on Windows. (Defaults is 0E-2A)
    macPrefix: "0E-2A"
    ? Wireguard Configs

    #UDP listen port used with IPv6
    backendPortv6: 51821
    #Pre shared key to use
    psk: 0
    #IP version to use on Wireguard
    tunnelMode: "separate"
    #Persistent keep interval to use
    keepaliveInterval: 0

Terraform​

Use the following Terraform snippet to reference the Flannel CNI pack in your Terraform template.

data "spectrocloud_registry" "public_registry" {
  name = "Public Repo"
}

data "spectrocloud_pack_simple" "flannel" {
  name    = "cni-flannel"
  version = "0.23.0"
  type = "helm"
  registry_uid = data.spectrocloud_registry.public_registry.id
}

Reference​