Which command enables IPv6 on an interface without manually configuring an IPv6 address?

The command that enables IPv6 on an interface without requiring manual configuration of an IPv6 address is "ipv6 enable." This command is specifically designed to activate IPv6 processing on an interface. When you enter this command, it allows the interface to participate in the IPv6 routing protocols and enables the interface to automatically generate a link-local address, which is crucial for IPv6 communication.

By using "ipv6 enable," you can quickly and efficiently prepare an interface for IPv6 connectivity, particularly in environments where DHCPv6 or Stateless Address Autoconfiguration (SLAAC) will provide the necessary global or unique local addresses later on. It effectively sets the stage for further IPv6 configuration and ensures that the interface can begin interacting with other IPv6-enabled devices, which is essential for proper network functionality in an IPv6 environment.