Kubernetes - Fail to Install Flannel Network on Windows Node When Node has More Than One Network Interfaces

Kubernetes, the popular container orchestration platform, is known for its flexibility and scalability. However, like any sophisticated system, it can encounter challenges, especially when dealing with diverse environments. One common issue that users face is the failure to install Flannel network on a Windows node when that node has more than one network interface. In this article, we will delve into the root of the problem and provide step-by-step instructions to overcome this hurdle.

Understanding the Issue:

When a Windows node has multiple network interfaces, Kubernetes might encounter difficulties in determining which interface to use for Flannel networking. This can result in the installation process failing, leading to a breakdown in communication between nodes.

Checking Network Interfaces:

Before diving into solutions, it's crucial to identify the network interfaces available on the Windows node. Execute the following command in PowerShell to list the network interfaces:

Get-NetAdapter

This command will display a list of network interfaces along with their details, such as InterfaceIndex, InterfaceDescription, and Name.

Selecting the Correct Interface:

Once you've identified the network interfaces, it's necessary to specify the correct one for Flannel. You can do this by setting the --iface flag during the Flannel installation. For example:

.lanneld.exe --iface="Ethernet 1"

Replace "Ethernet 1" with the name of the desired network interface.

Modifying Kubernetes Configuration:

To ensure Kubernetes uses the specified network interface, update the Kubernetes configuration file. Open the kubelet configuration file (usually located at C:\Kubernetes\kubelet\kublet.exe.config) and add the following line under <configSections>:

<add key="flannel_iface" value="Ethernet 1" />

Again, replace "Ethernet 1" with the actual name of the network interface.

Restarting Services:

After making these changes, restart the Flannel and Kubernetes services to apply the modifications. Use the following commands:

Restart-Service Flannel
Restart-Service kubelet

Verifying Configuration:

To ensure everything is working as expected, use the following commands to verify the Flannel configuration:

Get-Service flanneld
Get-Service kubelet

If both services show a status of "Running," your Flannel installation on the Windows node should now be successful.

Additional Considerations:

• Firewall Settings: Ensure that the necessary ports for Flannel communication are open in the Windows Firewall.

• Network Policies: Review your network policies and adjust them if necessary to accommodate multiple network interfaces.

In the dynamic world of Kubernetes, overcoming installation challenges is part of the journey. By carefully selecting the network interface and updating the configuration, you can successfully install Flannel on a Windows node with multiple network interfaces. Remember to consider additional factors like firewall settings and network policies to ensure a seamless Kubernetes experience.