https://stackoverflow.com/questions/76065221/hostname-in-task-error-undefined-how-to-reference-nested-element-in-dictionary?noredirect=1#comment134150467_76065221

session.txt

$ tree 
.
├── inventories
│   └── demo
│       ├── hosts
│       └── host_vars
│           ├── CEASF-RTR.yml
│           └── cowfm-311-core.yml
└── playbook.yml

3 directories, 4 files

$ cat inventories/demo/hosts 
[CEASF]
CEASF-RTR

[CO311CORE]
cowfm-311-core

[ios:children]
CEASF
CO311CORE

$ cat inventories/demo/host_vars/CEASF-RTR.yml 
---
wired_dhcp_interfaces:
 - "GigabitEthernet0/0.1"
 - "GigabitEthernet0/0.4"
 - "GigabitEthernet0/0.5"

$ cat inventories/demo/host_vars/cowfm-311-core.yml 
---
wired_dhcp_interfaces:
  - "Vlan1"
  - "Vlan98"
  - "Vlan100"
  - "Vlan102"
  - "Vlan104"

$ cat playbook.yml 
---
- hosts: ios
  gather_facts: false

  tasks:
    - debug:
        var: wired_dhcp_interfaces

$ ansible-playbook -i inventories/demo/ playbook.yml 

PLAY [ios] *********************************************************************************************************************************

TASK [debug] *******************************************************************************************************************************
ok: [CEASF-RTR] => {
    "wired_dhcp_interfaces": [
        "GigabitEthernet0/0.1",
        "GigabitEthernet0/0.4",
        "GigabitEthernet0/0.5"
    ]
}
ok: [cowfm-311-core] => {
    "wired_dhcp_interfaces": [
        "Vlan1",
        "Vlan98",
        "Vlan100",
        "Vlan102",
        "Vlan104"
    ]
}

PLAY RECAP *********************************************************************************************************************************
CEASF-RTR                  : ok=1    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
cowfm-311-core             : ok=1    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0