Which CLI mode must be used to configure the BGP keychain in Cisco IOS XR software?

In Cisco IOS XR, BGP keychain configuration, which defines cryptographic authentication for BGP sessions, is executed from the global configuration mode (`configure`). This allows for the creation and management of keychains that can then be referenced by various routing protocols, including BGP, for authentication purposes.

Routing configuration mode is typically for configuring routing protocols themselves, not for system-wide security features like keychains that can be used by multiple protocols.

BGP neighbor configuration mode is too specific; keychains are a more general authentication mechanism configured outside of individual neighbor settings.

BGP address-family configuration mode is for specific address family settings for BGP, not for the underlying authentication mechanism like keychains.