What command sets the authentication method for VRRP to MD5 with a key string?

The command that correctly sets the authentication method for VRRP (Virtual Router Redundancy Protocol) to MD5 with a specified key string is structured to align with the syntax defined in the Cisco IOS command reference. The correct command indicates the specific VRRP group (in this case, group 1), and it explicitly states the use of MD5 as the authentication type followed by the keyword "key-string" to designate the actual key being used.

Using "vrrp 1 authentication md5 key-string Cisco123" clearly defines that the VRRP group is to use MD5 for authentication, and "key-string" is a critical term that identifies the follow-up string as the key, which is necessary for the protocol to operate securely. This setup ensures that all routers participating in the VRRP group will use the same authentication mechanism, contributing to the overall security of the routing environment.

The other command structures do not properly reflect the required syntax for configuring VRRP authentication with MD5. Each one either misplaces keywords or fails to include necessary components that denote the authentication type and key string clearly. Understanding the exact requirements of VRRP command syntax is essential in implementing it correctly to ensure proper redundancy and authentication in network configurations.