Metallb can have several address-pool configured.
In this case, Traefik randomly selects an address-pool to use for External-IP.
To configure Traefik to use a correct predefined Metallb's address-pool, we need to add to Traefik's addon configuration in cluster.yaml a corresponded annotation, like this:
- name: traefik enabled: true values: | service: annotations: metallb.universe.tf/address-pool: mypoolname