The ipv6 unicast-routing command is the fundamental global configuration command required to enable the IPv6 protocol stack on a RUCKUS ICX device. This command activates the device's ability to process and forward IPv6 unicast packets between its configured interfaces, effectively turning it into an IPv6 router. Without this command, the device will not perform Layer 3 forwarding for IPv6 traffic, even if IPv6 addresses are configured on its interfaces. It is the prerequisite for all other IPv6 routing functions.

A. ipv6 dhcp6-server enable: This command enables the DHCPv6 server service on the device. It is a specific application-level feature and does not enable the core IPv6 routing functionality.

C. ipv6 multicast: This command specifically enables IPv6 multicast routing protocols like PIM-SM. It is a separate feature from unicast routing and requires unicast routing to be enabled first.

D. ipv6 nd proxy: This enables the Neighbor Discovery (ND) proxy feature, a specialized function for specific network designs. It does not enable the global IPv6 routing capability.

1. RUCKUS FastIron Layer 3 Routing Configuration Guide, 08.0.95

Page 439, Section: "Enabling IPv6 routing": "To enable IPv6 routing on a Layer 3 switch, enter the ipv6 unicast-routing command at the global CONFIGURATION level of the CLI. This command globally enables IPv6 routing."

2. RUCKUS FastIron Command Reference, 08.0.95

Page 1688, Command: ipv6 unicast-routing: "This command enables IPv6 routing on a Layer 3 switch... By default, IPv6 routing is disabled on the device. You must enable IPv6 routing before the device can forward IPv6 packets."

3. RUCKUS Campus Fabric Configuration Guide, 08.0.95

Page 411, Section: "Configuring IPv6": The guide details IPv6 configuration steps, starting with the prerequisite of enabling IPv6 routing globally using the ipv6 unicast-routing command before any other IPv6 routing features can be configured.