1. If authentication is configured on the interface, the authentication mode configured on the interface is adopted.

2. If the authentication mode configured on the interface is null, the interface is not authenticated.

Please note: The null type does not mean that no authentication is configured.. :)

3. If no authentication is configured on the interface, the authentication mode configured on the area is adopted.

4. If no authentication mode is configured on the area either, no OSPF authentication is performed.

Good to know it!

nice job

useful information

good post

good to know

useful document, thanks