diff --git a/ee/ucp/kubernetes/kubernetes-network-encryption.md b/ee/ucp/kubernetes/kubernetes-network-encryption.md index 745174651e..dcee2cf0d4 100644 --- a/ee/ucp/kubernetes/kubernetes-network-encryption.md +++ b/ee/ucp/kubernetes/kubernetes-network-encryption.md @@ -35,6 +35,18 @@ Kubernetes Network Encryption is supported for the following platforms: * Only supported when using UCP’s default Calico CNI plugin * Supported on all Docker Enterprise supported Linux OSes +## Configuring MTUs + +Before deploying the SecureOverlay components one must ensure that Calico is configured so that the IPIP tunnel MTU leaves sufficient headroom for the encryption overhead. Encryption adds 26 bytes of overhead but every IPSec packet size must be a multiple of 4 bytes. IPIP tunnels require 20 bytes of encapsulation overhead. So the IPIP tunnel interface MTU must be no more than “EXTMTU - 46 - ((EXTMTU - 46) modulo 4)” where EXTMTU is the minimum MTU of the external interfaces. An IPIP MTU of 1452 should generally be safe for most deployments. + +Changing UCP’s MTU requires updating the UCP configuration. This process is described here. The user must update the following values to the new MTU: + + [cluster_config] + ... + calico_mtu = "1452" + ipip_mtu = "1452" + ... + ## Configuring SecureOverlay Once the cluster nodes’ MTUs are properly configured, deploy the SecureOverlay components using the Secure Overlay YAML file to UCP.