Abnormal Node Communication After OVS Network Plane Is Deployed for Kubernetes

Symptom

After the OVS plane is deployed on Kubernetes, the displayed network bandwidth is 0 when iperf/qperf services are running.

Key Process and Cause Analysis

By default, the network interface MTU in the container is 1500 bytes, which is the same as that of the host. After data packets are sent from the container, the data packets are encapsulated in the GRE/VXLAN overlay mode on the host OVS bridge. After the encapsulation, the data packets exceed 1500 bytes. As a result, the host fails to send network packets.

Conclusion and Solution

Set the network interface MTU in the container to 1400. For example:

ifconfig eth0 mtu 1400

In Kubernetes, the network configuration is usually managed by a CNI plugin. Therefore, if you are using a CNI plugin, read the documentation of the plugin to see how to configure the MTU value.