Automate multiple subnet creation using SubnetPool¶

Before creating an L2 template, ensure that you have the required subnets that can be used in the L2 template to allocate IP addresses for the managed cluster nodes. You can also create multiple subnets using the SubnetPool object to separate different types of network traffic. SubnetPool allows for automatic creation of Subnet objects that will consume blocks from the parent SubnetPool CIDR IP address range. The SubnetPool blockSize setting defines the IP address block size to allocate to each child Subnet. SubnetPool has a global scope, so any SubnetPool can be used to create the Subnet objects for any namespace and for any cluster.

To automate multiple subnet creation using SubnetPool:

Log in to a local machine where your management cluster kubeconfig is located and where kubectl is installed.

Note

The management cluster kubeconfig is created during the last stage of the management cluster bootstrap.
Create the subnetpool.yaml file with a number of subnet pools:

Note

You can define either or both subnets and subnet pools, depending on the use case. A single L2 template can use either or both subnets and subnet pools.
```
kubectl --kubeconfig <pathToManagementClusterKubeconfig> apply -f <SubnetFileName.yaml>
```
Note

In the command above and in the steps below, substitute the parameters enclosed in angle brackets with the corresponding values.

Example of a subnetpool.yaml file:
```
apiVersion: ipam.mirantis.com/v1alpha1
kind: SubnetPool
metadata:
  name: kaas-mgmt
  namespace: default
  labels:
    kaas.mirantis.com/provider: baremetal
    kaas.mirantis.com/region: region-one
spec:
  cidr: 10.10.0.0/16
  blockSize: /25
  nameservers:
  - 172.18.176.6
  gatewayPolicy: first
```
For the specification fields description of the SubnetPool object, see SubnetPool spec.
Verify that the subnet pool is successfully created:
```
kubectl get subnetpool kaas-mgmt -oyaml
```
In the system output, verify the status fields of the subnetpool.yaml file. For the status fields description of the SunbetPool object, see SubnetPool status.
Proceed to creating an L2 template for one or multiple managed clusters as described in Create L2 templates. In this procedure, select the exemplary L2 template for multiple subnets that contains the l3Layout section.

Caution

Using the l3Layout section, define all subnets of a cluster. Otherwise, do not use the l3Layout section. Defining only part of subnets is not allowed.