a.yaml

---
- name: a
  hosts: localhost
  become: yes
  tasks:
    - name: check passed data
      debug:
        msg: "Finding the interface assigned {{ keepalived.virtual_ip }}"

    - name: set interface fact
      set_fact:
        interface: "{{ item }}"
      when:
        - ansible_facts[item].ipv4 is defined
        - ansible_facts[item].ipv4.address == keepalived.virtual_ip
      with_items:
        - "{{ ansible_interfaces }}"
    
    - name: result
      debug:
        var: interface