If the interface you use for Kubernetes management traffic (for example, the IP address used for kubeadm join) is not the one that contains the default route out of the host, then you need to specify the management node IP address in the Kubelet config file. Add the following line to: (/etc/systemd/system/kubelet.service.d/10-kubeadm.conf):
Environment="KUBELET_EXTRA_ARGS=--fail-swap-on=false --node-ip=<node-management-ip-address>"
Consider a 2 node deployment where each node is connected to 2 networks - 10.0.2.0/24 and 192.168.56.0/24, and the default route on each node points to the interface connected to the 10.0.2.0/24 subnet. We want to use subnet 192.168.56.0/24 for Kubernetes management traffic. Assume the addresses of nodes connected to 192.168.56.0/24 are 192.168.56.105 and 192.168.56.106.
On the 192.168.56.105 node you add the following line to 10-kubeadm.conf:
Environment="KUBELET_EXTRA_ARGS=--fail-swap-on=false --node-ip=192.168.56.105"
On the 192.168.56.106 node you add the following line to 10-kubeadm.conf:
Environment="KUBELET_EXTRA_ARGS=--fail-swap-on=false --node-ip=192.168.56.106"