Which command enables 802.1X globally on a Cisco switch?

The `dot1x system-auth-control` command is used in global configuration mode on a Cisco switch to globally enable 802.1X port-based authentication across the entire switch. This command activates the fundamental 802.1X functionality that can then be applied and configured on individual interfaces.

`dot1x pae authenticator` is an interface-level command used to configure the Port Access Entity (PAE) role on a specific port, not to enable 802.1X globally.

`authentication port-control auto` is an interface-level command that sets the authentication control mode for a specific port to automatically authenticate devices, rather than a global enablement command.

`aaa new-model` enables the new Authentication, Authorization, and Accounting (AAA) model, which is a necessary prerequisite for many advanced security features like 802.1X, but it does not directly enable 802.1X itself.