With default DNS lookup enabled on a router, what occurs when a URL is entered at the CLI?

When a URL (like a hostname) is typed into the Cisco IOS CLI and DNS lookup is enabled (which it is by default), the router interprets this as an attempt to resolve a hostname to an IP address. It then tries to contact a configured DNS server to perform this resolution. If no DNS server is configured or reachable, or if the hostname cannot be resolved, the router will typically display a message indicating an unknown command or an unresolved hostname. It does not continuously attempt resolution indefinitely; there's usually a timeout. It also doesn't initiate a ping request or prompt for an IP address; its primary action is to use DNS for name resolution.