Pods not able to connect to kube-apiserver

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Environment

SUSE Caas Platform

Situation

In CaaS Platform, pods cannot communicate to kube-apiserver.

e.g. kured prints the following error:

time="2020-06-02T12:42:22Z" level=fatal msg="Error testing lock: Get https://10.96.0.1:443/apis/apps/v1/namespaces/kube-system/daemonsets/kured: dial tcp 10.96.0.1:443: i/o timeout"

The keywords in above error message are:

dial tcp 10.96.0.1:443: i/o timeout

Above error indicates that kured pod is not able to access the kubernetes default service.

Resolution

IPv4 forwarding needs to be enabled on all CaaS Platform machines. This can be changed without having to reboot by running the following:

sysctl -w net.ipv4.ip_forward=1

For persistence after reboot, add the following to /etc/sysctl.conf or to conf file in /etc/sysctl.d:

net.ipv4.ip_forward = 1

Cause

The issue could occur due to several reasons. One such reason is that IPv4 forwarding is disabled on nodes. IPv4 forwarding needs to be enabled on all CaaS Platform machines.

Disclaimer

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