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How to choose network interface and IP address for VIP

Andrey Dyatlov
  • Updated

Problem

Kubernetes API is not available via virtual IP address (VIP).

Solution

When you install the cluster with the dkp createcommand, ensure that

  • the control plane nodes are in the same subnet and layer-2 network
  • virtual IP address (--control-plane-endpoint) is a free IP address from that subnet
  • network interface for Virtual IP address (--virtual-ip-interface) is the same interface on which kube-apiserver listens. kube-apiserver listens on a default interface. You can use the following command to find the default interface: route | grep default
  • L2 switches in your infrastructure do not block Gratuitous ARP packets. kube-vip uses Gratuitous ARP to advertise the virtual IP for the control plane; if the switch blocks these packets then fail-over between control plane nodes will not work.

Example

If we have the following networking configurations on the control plane nodes:

Control plane node 1:
eth0: 1.2.3.4/29
eth1: 10.1.2.1/24
Control plane node 2:
eth0: 5.6.7.8/25
eth1: 10.1.2.2/24
Control plane node 3:
eth0: 9.10.11.12/30
eth1: 10.1.2.3/24

then dkp create command should look like this:

dkp create cluster preprovisioned \
--cluster-name ${CLUSTER_NAME} \
--control-plane-endpoint-host 10.1.2.0 \
--virtual-ip-interface eth1