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Enable Overlay Network

Edge clusters are often deployed in locations where network environments are not managed by teams that maintain the edge deployments. However, a Kubernetes cluster, specifically several control plane components, require stable IP addresses. In the case of an extended network outage, it's possible that your cluster components would lose their original IP addresses when the cluster expects them to remain stable, causing the cluster to experience degraded performance or become non-operational.

Palette allows you to create a virtual overlay network on top of the physical network, and the virtual IP addresses of all cluster components are managed by Palette. Inside the cluster, the different components use the virtual IP addresses to communicate with each other instead of the underlying IP addresses that could change due to external factors. If the cluster experiences an outage with the overlay network enabled, components inside the cluster retain their virtual IP addresses in the overlay network, even if their IP addresses in the underlying physical network has changed, protecting the cluster from an outage.

VxLAN Overlay Architecture

tech preview
This is a Tech Preview feature and is subject to change. Do not use this feature in production workloads.

When Should You Consider Enabling Overlay Network?​

If your Edge clusters are deployed in network environments that fit the following descriptions, you should consider enabling an overlay network for your cluster:

  • Network environments with dynamic IP address management, such as a DHCP network.
  • Instable network environments or environments that are out of your control. For example, you are deploying an Edge host in a restaurant located in a commercial building, where the network is managed by the building and cannot be easily altered by your staff.
  • Environments where you expect your edge hosts to move from one physical location to another.

Example Scenario​

The Analytics team of a manufacturing company is deploying an Edge host to their assembly line to collect metrics from the manufacturing process. The building in which the Edge host is deployed has a network that is managed by a DHCP server. The region experiences a bad weather event that causes a sustained outage.

Without Overlay NetworkWith Overlay Network
Upon recovery, each Kubernetes component inside in the Edge host requests an IP address from the DHCP server, and receives a different IP address than their original IP address before the outage happened. Since Kubernetes expects several components in the control plane to have stable IP addresses, the cluster becomes non-operational and assembly line is unable to resume operationsEach Kubernetes component inside in the Edge host has a virtual IP address in the overlay network. Upon recovery, their IP addresses in the overlay network remain the same despite their IP addresses changing in the underlying DHCP network. The Edge host is able to assume its workload and the assembly line resumes operations

Limitations​

  • When adding multiple Edge hosts to an existing cluster with overlay enabled, failure to add one host will block the addition of the other hosts.

Prerequisites​

  • At least one Edge host registered with your Palette account.
  • Your cluster profile must have K3s or RKE2 as its Kubernetes distribution.
  • All Edge hosts must be on the same Layer-2 network.
  • Broadcast messages must be allowed between all Edge hosts participating in the cluster.
    • For Virtual Machine (VM) Edge hosts in VMware, this means features such as promiscuous mode must be enabled to allow broadcasts between hosts.
    • Switches cannot implement features that block broadcast between ports where Edge hosts are connected.
  • If you are launching your Edge hosts in virtual machine environments and you are using either Cilium or Flannel as your container network interface (CNI), ensure that you add the following commands in the user-data file at the boot stage. Replace INTERFACE_NAME with the name of the network interface on your Edge host. 
    stages:
      initramfs:
        - name: "Disable UDP segmentation"
          commands:
            - ethtool -K INTERFACE_NAME tx-udp_tnl-segmentation off
            - ethtool -K INTERFACE_NAME tx-udp_tnl-csum-segmentation off
    This is related to a known issue with VMware's VMXNET3 adapter, which is widely used in different virtual machine management services, including VMware vSphere and Hyper-V.

Enable Overlay Network​

You can enable an overlay network for your cluster during cluster creation.

warning

You will not be able to change the network overlay configurations after the cluster has already been created.

  1. Log in to Palette.

  2. Navigate to the left Main Menu and select Clusters.

  3. Click on Add New Cluster.

  4. Choose Edge Native for the cluster type and click Start Edge Native Configuration.

  5. Give the cluster a name, description, and tags. Click on Next.

  6. Select a cluster profile. If you don't have a cluster profile for Edge Native, refer to the Create Edge Native Cluster Profile guide. Click on Next after you have selected a cluster profile.

  7. In the Kubernetes layer of the cluster profile, add the parameter cluster.kubevipArgs.vip_interface and set its value to scbr-100:

    cluster:
      kubevipArgs:
        vip_interface: "scbr-100"

  8. In the network layer of your cluster profile, specify the name of the Network Interface Controllers (NIC) on your Edge hosts to be scbr-100. This is the name of the interface Palette creates on your Edge devices to establish the overlay network.

    The following are the sections of the packs you need to change depending on which CNI pack you are using:

    In the Calico pack YAML file default template, uncomment FELIX_MTUIFACEPATTERN and set its value to scbr-100 and uncomment manifests.calico.env.calicoNode.IP_AUTODETECTION_METHOD and set its value to interface=scbr-100.

    manifests:
        calico:
            ...
            env:
            # Additional env variables for calico-node
            calicoNode:
                #IPV6: "autodetect"
                FELIX_MTUIFACEPATTERN: "scbr-100"
                #CALICO_IPV6POOL_NAT_OUTGOING: "true"
                #CALICO_IPV4POOL_CIDR: "192.168.0.0/16"
                IP_AUTODETECTION_METHOD: "interface=scbr-100"

  9. Review the rest of your cluster profile values and make changes as needed. Click on Next.

  10. In the Cluster Config stage, toggle on Enable Overlay Network. This will prompt you to provide additional configuration for your virtual overlay network.

  11. In the Overlay CIDR Range field, provide a private IP range for your cluster to use. Ensure this range is not used by others in the same network environment. When you toggle on Enable Overlay Network, Palette provides a default range that is typically unused. We suggest you keep the default range unless you have a specific IP range you want to use.

warning

The overlay CIDR range cannot be changed after the cluster creation.

After you have provided the overlay CIDR, the VIP field at the top of the page will be grayed out, and the first IP address in the overlay CIDR range will be used as the Overlay VIP. This VIP is the internal overlay VIP used by the cluster.

  1. Finish the rest of the cluster configurations and click Finish Configuration to deploy the cluster. For more information, refer to Create Cluster Definition.

Validate​

  1. Log in to Palette.

  2. Navigate to the left Main Menu and select Clusters.

  3. Select the host cluster you created to view its details page.

  4. Select the Nodes tab. For each host, the Private Ips column lists an overlay IP address within the CIDR range you provided during cluster configuration.

tip

To view the external IP addresses of the edge hosts, from the Main Menu, go to Clusters, and click the Edge Hosts tab. The IP address displayed in the table is the external IP address.

Access Cluster with Overlay Network Enabled​

You can access a cluster with overlay network enabled in the following ways:

  • Access the cluster with kubectl CLI. For more information, refer to Access Cluster with CLI.
  • Access LoadBalancer services. You can provision LoadBalancer services in your Kubernetes cluster and expose them to external traffic. For example, refer to Publish Cluster Services with Kube-vip.
  • Access a node by IP address. You can use the node's external IP address to access the node directly. The overlay IP addresses are internal to the cluster itself and cannot be accessed from outside the cluster.

Resources​