Octet

Say this first

Resource modules manage one feature as structured data, for example cisco.ios.ios_vlans or ios_l3_interfaces, instead of raw CLI lines. The state decides how. merged adds or updates what you list and leaves the rest. replaced makes each listed item match exactly, removing attributes you left out. overridden makes the whole resource on the device match your list, which deletes anything not listed. deleted removes, and gathered, rendered and parsed read or convert without changing anything.

Go deeper

The states

State	Touches the device	Effect
`merged`	Yes	Add or update listed items; leave others alone
`replaced`	Yes	Listed items match exactly; unlisted items untouched
`overridden`	Yes	Whole resource matches the list; unlisted items removed
`deleted`	Yes	Remove listed items, or all if none listed
`gathered`	Reads	Return the current config as structured data
`rendered`	No	Return the CLI commands the config would produce, offline
`parsed`	No	Turn running-config text you supply into structured data

Example

YAML

- name: Access VLANs
  cisco.ios.ios_vlans:
    config:
      - vlan_id: 10
        name: USERS
      - vlan_id: 20
        name: VOICE
      - vlan_id: 30
        name: GUESTS
    state: merged

The result holds before, after and commands. If only VLAN 30 is new, commands is ["vlan 30", "name GUESTS"].

Why they beat ios_config lines

The module understands the feature, so it knows that shutdown is the opposite of no shutdown, removes attributes correctly in replaced, and stays idempotent without you matching running-config text.

They will ask next

When would you use overridden?
When the source of truth is complete for that resource and the device must match it exactly, such as the VLAN list on a leaf switch. Run it in check mode first: a missing VLAN in your data deletes a VLAN in production.
How do resource modules help with brownfield onboarding?
gathered pulls today's config as structured data you can store as variables, and parsed does the same from saved config backups without touching the device. That gives you a starting data model that matches reality.

Traps

Using overridden with incomplete data. It removes everything you did not list.
Assuming replaced removes unlisted VLANs. It only rewrites the ones you list.

How did you do?