installer/docs/user/openstack/deploy_dual_stack_cluster.md

Creating a dual-stack cluster on OpenStack

Table of Contents

• Prerequisites
• Creating DualStack Networks for the cluster
• Creating DualStack API and Ingress VIPs Ports for the cluster
• Deploy OpenShift

Prerequisites

• Installation with dual-stack is only allowed when using one OpenStack network with one IPv4 and IPv6 subnet.
• API and Ingress VIPs ports needs to pre-created by the user and the addresses specified in the install-config.yaml.
• Add the IPv6 Subnet to a neutron router to provide router advertisements.
• The dualstack network MTU must accomodate the minimun MTU for IPv6, which is 1280, and OVN-Kubernetes encapsulation overhead, which is 100.

Additional prerequisites are listed at the OpenStack Platform Customization docs

Note: Converting a IPv4 single-stack cluster to a dual-network cluster network is not supported by OpenStack.

Creating Dual-Stack Networks for the cluster

You must create one network and add one IPv4 subnet and another IPv6 subnet with either slaac, stateless or stateful modes. Here is an example:

$ openstack network create --project <project-name> --share --external --provider-physical-network <physical-network> --provider-network-type flat dualstack
$ openstack subnet create --project <project-name> subnet-v4 --subnet-range 192.168.25.0/24 --dhcp --dns-nameserver <nameserver> --network dualstack
$ openstack subnet create --project <project-name> subnet-v6 --subnet-range fd2e:6f44:5dd8:c956::/64 --dhcp  --network dualstack --ip-version 6 --ipv6-ra-mode slaac --ipv6-address-mode slaac

Given the above example uses a provider network, this network can be added to the router external gateway to enable external connectivity and router advertisements with the following command:

$ openstack router set --external-gateway dualstack <router-id>

Creating Dual-Stack API and Ingress VIPs Ports for the cluster

You must create the API and Ingress VIPs Ports with the following commands:

$ openstack port create api --network dualstack
$ openstack port create ingress --network dualstack

Deploy OpenShift

Now that the Networking resources are pre-created you can deploy OpenShift. Here is an example of install-config.yaml:

apiVersion: v1
baseDomain: mydomain.test
compute:
- name: worker
  platform:
    openstack:
      type: m1.xlarge
  replicas: 3
controlPlane:
  name: master
  platform:
    openstack:
      type: m1.xlarge
  replicas: 3
metadata:
  name: mycluster
networking:
  machineNetwork:
  - cidr: "192.168.25.0/24"
  - cidr: "fd2e:6f44:5dd8:c956::/64"
  clusterNetwork:
  - cidr: 10.128.0.0/14
    hostPrefix: 23
  - cidr: fd01::/48
    hostPrefix: 64
  serviceNetwork:
  - 172.30.0.0/16
  - fd02::/112
platform:
  openstack:
    ingressVIPs: ['192.168.25.79', 'fd2e:6f44:5dd8:c956:f816:3eff:fef1:1bad']
    apiVIPs: ['192.168.25.199', 'fd2e:6f44:5dd8:c956:f816:3eff:fe78:cf36']
    controlPlanePort:
      fixedIPs:
      - subnet:
          name: subnet-v4
      - subnet:
          name: subnet-v6
      network:
        name: dualstack

There are important things to note:

The subnets under platform.openstack.controlPlanePort.fixedIPs can contain both id or name. The same applies to the network platform.openstack.controlPlanePort.network.