Setup MetalLB L2 Advertisement configuration

Copy sample L2Advertisement configuration for MetalLB from the same documentation url (step #16)

or

Use single-nic-vlan-metallb-l2-advertisements.sample file.

Create a copy of sample config to create MetalLB L2 Advertisement configuration file.

cp single-nic-vlan-metallb-l2-advertisements.sample osp-ng-metallb-l2-advertisements.yaml

Edit the file for use with your preferred editor.
```
vi osp-ng-metallb-l2-advertisements.yaml
```
Change the configuration as per your setup. You may just need to chance the interface names as per the network configuration table.
Lastly, configure a L2Advertisement resource which will define which node advertises a service to the local network which has been preconfigured for your lab environment:
```
oc apply -f osp-ng-metallb-l2-advertisements.yaml
```

Verify the configuration:

oc get l2advertisements.metallb.io -n metallb-system

Sample output

NAME          IPADDRESSPOOLS    IPADDRESSPOOL SELECTORS   INTERFACES
ctlplane      ["ctlplane"]                                ["enp1s0"]
internalapi   ["internalapi"]                             ["enp1s0.20"]
storage       ["storage"]                                 ["enp1s0.21"]
tenant        ["tenant"]                                  ["enp1s0.22"]