The following are the options that you can use for configuring a switchport. These are taken from this Cisco documentation.
switchport mode access: Puts the interface (access port) into permanent nontrunking mode and negotiates to convert the link into a nontrunk link. The interface becomes a nontrunk interface, regardless of whether the neighboring interface is a trunk interface.
switchport mode dynamic auto: Makes the interface able to convert the link to a trunk link. The interface becomes a trunk interface if the neighboring interface is set to trunk or desirable mode. The default switchport mode for newer Cisco switch Ethernet interfaces is dynamic auto. Note that if two Cisco switches are left to the common default setting of auto, a trunk will never form.
switchport mode dynamic desirable: Makes the interface actively attempt to convert the link to a trunk link. The interface becomes a trunk interface if the neighboring interface is set to trunk, desirable, or auto mode. This is the default switchport mode on older switches, such as the Catalyst 2950 and 3550 Series switches.
switchport mode trunk: Puts the interface into permanent trunking mode and negotiates to convert the neighboring link into a trunk link. The interface becomes a trunk interface even if the neighboring interface is not a trunk interface.
switchport nonegotiate: Prevents the interface from generating DTP frames. You can use this command only when the interface switchport mode is access or trunk. You must manually configure the neighboring interface as a trunk interface to establish a trunk link.
Now the terminology used to describe the configuration as “ON” and “ON” is an unfortunate and confusing use of a terminology that is more often used for etherchannel. Etherchannel also has an autoconfiguration feature where you can configure the etherchannel on both ends with any of the following commands:
channel-group 1 mode on
channel-group 1 mode auto
channel-group 1 mode desirable
The first of these commands hardwires etherchannel to function without negotiation. This is an “ON” and “ON” configuration situation.
Once again, unfortunately, the same terminology is used for Dynamic Trunking Protocol (DTP). To answer your question, an “ON and ON” configuration simply means nothing more than configuring both ends of the trunk as
switchport mode trunk and using the
switchport nonegotiate command on both ends of the trunk.
I hope this has been helpful!