Set the MTU size for Calico

Available since MCC 2.24.0 (14.0.0, 14.0.1, 15.0.1) TechPreview

You can set the maximum transmission unit (MTU) size for Calico in the Cluster object using the calico.mtu parameter. By default, the MTU size for Calico is 1450 bytes. You can change it regardless of the host operating system.

For details on how to calculate the MTU size, see Calico documentation: Configure MTU to maximize network performance.

The following configuration example of the Cluster object covers a use case where the interface MTU size of the workload network, which is the smallest value across cluster nodes, is set to 9000 and the use of WireGuard is not expected:

spec:
  ...
  providerSpec:
    value:
      ...
      calico:
        mtu: 8950

Note

Since Container Cloud 2.29.0 (Cluster releases 17.4.0 and 16.4.0), WireGuard is deprecated. If you still require the feature, contact Mirantis support for further information.

Caution

If you do not expect to use WireGuard encryption, ensure that the MTU size for Calico is at least 50 bytes smaller than the interface MTU size of the workload network. IPv4 VXLAN uses a 50-byte header.

Warning

Mirantis does not recommend changing this parameter on a running cluster. It leads to sequential draining of nodes and re-installation of packets, as during cluster upgrade.