1. metallb watch object in k8s, if there is a new LB service, it will provide a IP from its pool.
  2. two mode, Layer2 and BGP 
    - peer-address: <router1>
  peer-asn:65000
  my-asn:65009
address-pools:
- name: default
  protocol: bgp
  addresses:
  - 192.168.10.0/24
  3. components 
    controller: is responsible for arranging ip address and service/endpoint listening
speaker: make sure service ip reachable.