The node to announce the L2 service should be selected based on the L2 advertisement that completely matches the ipaddresspool selector and the ipaddress pool.

Two l2 advertisements that have ip addresspools selected on label (zone=east) but one has specific ip address pool while the other does not have.
Service is created requesting ip addresspool that is not specified in any of the advertisement.

4.12

Always

1. Create two ip address pools - ipaddresspool-a and ipaddress-pool-b both with label zone=east
-----
oc get ipaddresspool ipaddresspool-a -n openshift-operators -oyaml
apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  creationTimestamp: "2022-09-29T19:17:35Z"
  generation: 1
  labels:
    zone: east
  name: ipaddresspool-a
  namespace: openshift-operators
  resourceVersion: "8283505"
  uid: 28e234cc-acea-422f-b590-173b8ec4c34d
spec:
  addresses:
  - 192.168.216.101-192.168.216.150
  autoAssign: true
  avoidBuggyIPs: false

 oc get ipaddresspool ipaddresspool-b -n openshift-operators -oyaml
apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  creationTimestamp: "2022-09-29T19:17:42Z"
  generation: 1
  labels:
    zone: east
  name: ipaddresspool-b
  namespace: openshift-operators
  resourceVersion: "8317966"
  uid: b8ea254b-20e2-4062-b2e4-62b98d6e28fb
spec:
  addresses:
  - 192.168.216.151-192.168.216.200
  autoAssign: true
  avoidBuggyIPs: false


 2. Create two l2advertisements one with ipaddresspool selector & ip addresspool and other with just ip addresspool selector announcing service on different set of nodes.

oc get l2advertisements l2-adv-east -n openshift-operators -oyaml
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
  creationTimestamp: "2022-09-29T19:33:42Z"
  generation: 2
  name: l2-adv-east
  namespace: openshift-operators
  resourceVersion: "8318763"
  uid: 7a0c23ce-e7a6-46db-a81f-0ccab7adf9e0
spec:
  ipAddressPoolSelectors:
  - matchExpressions:
    - key: zone
      operator: In
      values:
      - east
  ipAddressPools:
  - ipaddresspool-a
  nodeSelectors:
  - matchExpressions:
    - key: kubernetes.io/hostname
      operator: In
      values:
      - worker000-r650
      - worker001-r650
      - worker002-r650
      - worker003-r650
      - worker004-r650
      - worker005-r650

oc get l2advertisements l2-adv-west -n openshift-operators -oyaml
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
  creationTimestamp: "2022-09-29T19:34:59Z"
  generation: 2
  name: l2-adv-west
  namespace: openshift-operators
  resourceVersion: "8329049"
  uid: 26f4b83c-2cf4-4b73-a404-bf463900bdb8
spec:
  ipAddressPoolSelectors:
  - matchExpressions:
    - key: zone
      operator: In
      values:
      - east
  nodeSelectors:
  - matchExpressions:
    - key: kubernetes.io/hostname
      operator: In
      values:
      - worker006-r650
      - worker008-r650
      - worker009-r650
      - worker010-r650
      - worker011-r650


 3. Create a service requesting address from ipaddresspool-b.
oc get svc hello-idle -oyaml
apiVersion: v1
kind: Service
metadata:
  annotations:
    metallb.universe.tf/address-pool: ipaddresspool-b
  creationTimestamp: "2022-09-29T20:28:51Z"
  name: hello-idle
  namespace: a1
  resourceVersion: "8329276"
  uid: cd181150-b4fc-4c8a-bdda-c5c03f91c5e2
spec:
  allocateLoadBalancerNodePorts: true
  clusterIP: 172.30.8.149
  clusterIPs:
  - 172.30.8.149
  externalTrafficPolicy: Cluster
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - nodePort: 31586
    port: 8000
    protocol: TCP
    targetPort: 8080
  selector:
    name: hello-idle
  sessionAffinity: None
  type: LoadBalancer
status:
  loadBalancer:
    ingress:
    - ip: 192.168.216.151


oc get events
LAST SEEN   TYPE     REASON             OBJECT                             MESSAGE
37m         Normal   Scheduled          pod/hello-idle-c4pt5               Successfully assigned a1/hello-idle-c4pt5 to worker002-r650 by master-2
37m         Normal   AddedInterface     pod/hello-idle-c4pt5               Add eth0 [10.129.6.16/23] from ovn-kubernetes
37m         Normal   Pulled             pod/hello-idle-c4pt5               Container image "quay.io/openshifttest/hello-pod@sha256:04b6af86b03c1836211be2589db870dba09b7811c197c47c07fbbe33c7f80ef7" already present on machine
37m         Normal   Created            pod/hello-idle-c4pt5               Created container hello-idle
37m         Normal   Started            pod/hello-idle-c4pt5               Started container hello-idle
37m         Normal   Scheduled          pod/hello-idle-rqjbk               Successfully assigned a1/hello-idle-rqjbk to worker011-r650 by master-2
37m         Normal   AddedInterface     pod/hello-idle-rqjbk               Add eth0 [10.131.0.235/23] from ovn-kubernetes
37m         Normal   Pulled             pod/hello-idle-rqjbk               Container image "quay.io/openshifttest/hello-pod@sha256:04b6af86b03c1836211be2589db870dba09b7811c197c47c07fbbe33c7f80ef7" already present on machine
37m         Normal   Created            pod/hello-idle-rqjbk               Created container hello-idle
37m         Normal   Started            pod/hello-idle-rqjbk               Started container hello-idle
37m         Normal   IPAllocated        service/hello-idle                 Assigned IP ["192.168.216.151"]
37m         Normal   SuccessfulCreate   replicationcontroller/hello-idle   Created pod: hello-idle-c4pt5
37m         Normal   SuccessfulCreate   replicationcontroller/hello-idle   Created pod: hello-idle-rqjbk
2m35s       Normal   nodeAssigned       service/hello-idle                 announcing from node "worker002-r650" with protocol "layer2"

Node selected ( worker002-r650) to announce the L2 service IP is from l2-adv-east. l2-adv-east has both ipaddresspool selector + ip address pool (ipaddresspool-a)

Node selected to announce L2 service IP should be from l2-adv-west that matches the ipaddresspool selector label.

ipaddresspool selector AND ip addresspool both should be considered if l2advertisement is created with both values.